CM. Shchipitsyn
General Director of System Sensor Fire Detectors LLC
In case of fire, the warning system is the link between the automatic fire alarm system and people. At first glance, bells, strobes and sirens seem to be the simplest components of a warning system, but in public and administrative buildings they are the only source of signals that call for people to evacuate immediately.
The article presents the requirements of Russian and foreign regulatory documents to such systems practical recommendations on the placement of sirens, as well as the latest technologies for determining the exit path using a guiding audio signal.
Russian regulatory requirements
The general procedure for designing fire warning systems is defined in NPB 104-03 "Warning systems and management of evacuation of people during fires in buildings and structures." The standards provide for 5 types of warning and evacuation control systems (WEC), depending on the notification method, dividing the building into warning zones and other characteristics. Sound or light and sound warning methods in the form of sirens and stroboscopes are used in the most simple systems Type 1 and 2 alerts.
The characteristics of the sirens must comply with the requirements of NPB 77-98 "Technical means of warning and fire evacuation control. General technical requirements. Test methods" According to the classification given in the document, sirens are divided into light, sound, speech and combined sound pressure level developed by sound sirens at distance 1 ± 0.05 m, should be set within 85-110 dB.
According to NPB 104-03, sound signals of SOUE must provide the sound level:
Wall-mounted sounders (Fig. 1), as a rule, must be mounted at a height of at least 2.3 m from the floor level and at least 15 cm from the ceiling. In rooms where people are in noise-protective equipment or with a noise level of more than 95 dB, sound annunciators must be combined with light ones; the use of flashing light annunciators is allowed. Lighted or flashing alarms are also used in buildings occupied by deaf and hard of hearing people.
Degree of protection technical means notification provided by the shell in accordance with GOST 14254 must be at least IP 41.
Foreign requirements for warning systems
The requirements of domestic standards for many components of fire alarm systems practically coincide with the national standards of other countries, but significant differences remain for warning systems.
In European systems, a minimum alarm level of 65 dB is allowed, with a reduction to 60 dB in rooms of less than 60 m2, at staircase landings and at certain points limited space(Fig. 2, a), in rooms with operating equipment, it is sufficient to exceed the noise level by 5 dB (Fig. 2, b), and not by 15 dB, as in Russian standards. In sleeping quarters (Fig. 2, c) the signal level at the level of the head of a sleeping person should be 75 dB, in contrast to the Russian 70 dB.
According to NFPA72 (US National Fire Code, 1993 edition), sounders are installed within almost the same limits - at least 90" from the floor level and at least 6" from the ceiling (1" = 25.4 mm) When installing combined strobe light and sound devices, this requirement is replaced by the corresponding requirement for the installation of strobe devices.
In rooms with operating mechanical equipment, an alarm signal level of at least 85 dB must be provided, as opposed to a level of 75 dB for other rooms. In NFPA72, in addition to the “general” operating mode of the alarm system, the so-called address mode is regulated. It is used for posts of nurses on duty, security services, etc. The requirements for it are significantly lower: the alert signal level is at least 10 dB above the average background noise level and at least 5 dB above the maximum noise level lasting at least 60 s, but not less than 45 dB. These requirements can be used as a guide when calculating a system for alerting service personnel using warning signals about a fire hazard, generated, for example, by addressable analogue and laser aspiration SPS. Most modern sound alarms from the world's leading manufacturers have the ability to adjust the sound level.
Sound warning systems
Type of sound signals of fire alarms
According to NPB 104-03, sound warning signals must differ in tone from sound signals for other purposes. In NFPA72, in order to eliminate the possibility of incorrect interpretation of the alarm signal, the type of sound signal used in fire alarm systems is standardized. The type of signal is periodic, each period is 4 s and consists of 3 pulses with pauses: sound signal 0.5 s, pause 0.5 s, sound signal 0.5 s, pause 0.5 s, sound signal 0.5 s, pause 1.5 s (Fig. 3). According to NFPA72, the total minimum signal duration is 180 s; according to NPB 104-03, the SOUE must operate for the time necessary to complete the evacuation of people from the building.
Location of sounders
The number of sound fire alarms, their placement and power must ensure the sound level in all places of permanent or temporary residence of people in accordance with the requirements of NPB 104-03. The initial data for calculation in the simplest case are the dimensions of the room and the minimum required level of sound signals, which is determined by the type of room (sleeping or working), the permissible noise level in it, etc. The table shows typical noise levels from the most common sources.
For example, for a sleeping area with exhaust fan the level of the required alert signal must not be lower than (55 + 15) = 70 dB. To do this, the siren signal must exceed the specified value by the amount of attenuation when it propagates to the most remote part of the room. The signal level at an arbitrary distance is determined by adding the rated value of the siren signal (at 1 m) with the value of signal attenuation (with a minus sign) for a given distance . The amount of signal attenuation in dB at a distance L in meters, relative to its value at a distance of 1 m from the siren, can be calculated using the formula:
Thus, if a siren at a distance of 1 m provides a signal level of 100 dB, then at 10 m the attenuation is -20 dB and the signal level is 80 dB.
When using several sirens in one room, it is necessary to take into account that the magnitude of two equal signals during in-phase addition increases by 2 times, that is, by only 3 dB. When using one siren for several rooms, it is necessary to take into account the weakening of the signal when passing through the doors. According to the European calculation method, in the general case, the signal attenuation is assumed to be -30 dB - for fire doors, -20 dB - for standard doors(Fig. 4).
Light warning systems
There are no detailed recommendations on the use of light and combined light and sound alarms in the domestic regulatory framework. To solve practical problems, you can turn to American regulatory requirements.
When choosing equipment and determining installation locations for light alarms, it is necessary to distinguish between the type of room: sleeping area; a room other than a bedroom or a corridor.
Location of warning lights in premises
NFPA72 sets very clear requirements for the total number of strobes and the distance between them, depending on the type of room, its size, the luminous intensity of the annunciator and its installation location. Diagram 1 for rooms other than bedrooms shows the minimum luminous intensity values for 1, 2 and 4 wall-mounted sirens.
When using two sirens, they must be installed on opposite walls; If more than two sirens are used, their light pulses must be synchronized. Synchronization of sirens in analogue addressable systems is carried out automatically; in traditional systems it is necessary to use an additional wire. In rooms measuring 80 x 80 feet (approximately 24.4 x 24.4 m) or larger, where there may be more than two sounders, the distance between installed devices must be a minimum of 55 feet (approximately 16.8 m).
In areas other than bedrooms, wall-mounted annunciators should be mounted on walls 80 to 96 inches from the floor and a minimum of 6 inches from the ceiling.
Requirements for ceiling light annunciators (Fig. 5) in terms of luminous intensity (in candelas) depending on the size of the room are shown in Diagram 2. These data can only be used when installing the strobe in the center of the room; in other cases, the level of luminous intensity should be determined based on the room , the dimensions of which are equal to twice the distance from the siren to the furthest wall. When ceiling heights exceed 30 feet (approximately 9 m), NFPA72 requires that sounders be installed either on walls or on special hangers so that the distance from the floor to the sounders does not exceed 30 feet.
The distances between individual system devices and the exact installation locations of stroboscopic light annunciators depend on the size and configuration of the protected area or area. The specified requirements are based on a basic calculation for a square-shaped room. The strobes are placed asymmetrically, but in such a way that each of them provides notification in one of the quarters of the room (Fig. b, a). For this example, the operation of the strobes must be synchronized. If you place the strobes in the centers of the walls, the signal level in the corners of the room will be unacceptably low (Fig. b, b). In rooms of any configuration, with the exception of corridors, for calculations according to diagram 2, one or more squares of a size are used that completely fits the room of a given shape.
For bedrooms, a luminous intensity of 110 candelas should be provided when installing the wall strobe at a distance of 24 inches (610 mm) or more from the ceiling, and 177 candelas when installed at a distance less than 24 inches (610 mm). Accordingly, the ceiling light annunciator must also provide a luminous intensity of 177 candelas. In any case, the gate should be installed no more than 16 feet (approximately 5 m) from the level of the pillow in the horizontal projection (Fig. 7).
Location of warning lights in corridors
For corridors, strobes producing 15 candelas of light should be installed no more than 15 feet from the ends of the corridor. Maximum distance the distance between two adjacent gates should not exceed 100 feet (approximately 30.5 m). Moreover, any parts of the corridor in which there is a violation of the continuity of view should be interpreted as separate corridors. Typical location of warning lights in corridors various types shown in Fig. 8.
Sound emergency exit signs
All audible signals used during evacuation are alarm signals; they do not provide information about the direction to the nearest fire exit or its location. Such a goal is not set when using them; it is only necessary to sound at the required level all the rooms where people can be.
The bulk of emergency exit signs (emergency lighting, markings, color code of walls and doors, photoluminescent guide strips, etc.) involve only visual perception. But such signs become ineffective if part of the building is completely or partially filled with smoke or a person has vision problems.
A natural solution is to use special types of sound. For example, a broadband pulsed noise signal with a continuous spectrum over the entire audio range is quasi-white noise. The source of such sound is easily and quickly determined by the human hearing, which makes this method an ideal means for ensuring rapid evacuation. Activated by an existing fire alarm system, a guidance sound source located at carefully selected points emits audible signals to help people find their way to emergency exits. Guiding sound technology is used by sound annunciators of the new ExitPoint class (Fig. 9).
The evacuation stage is transmitted by the frequency of pulses (pulsations) of the noise signal. The “fast” pulsation speed mode is used to indicate an evacuation exit, the “medium” speed mode is used to create the direction of movement of the evacuation exit, the “slow” pulsation mode indicates the exit from the interior of the building (Fig. 10). In the pauses between the emission of the noise guidance sound, voice information messages or additional sound signals can be played.
Messages (e.g., Exit, Stairs Up, Stairs Down, Cover Zone) or additional signals such as an increasing frequency siren (up up the stairs), decreasing frequency siren (down the stairs), the standard fire alarm sound is three single-frequency pulses with a pause (see Fig. 3). The appearance of additional sound signals allows a person to intuitively determine their meaning even in a stressful environment.
ExitPoint sound signs do not replace traditional sound and light alarms, but are used as auxiliary devices in the fire alarm system and speed up the process of evacuating people in the building. The sound signals of fire alarms have narrow spectra and practically do not interfere with the localization of broadband ExitPoint signals. When combined with a voice notification, it is possible to separate the notification by time, indicating in the text the technology for using ExitPoint guidance sound signals.
In conclusion, it should be noted that a competent approach to the process of designing a warning system in accordance with Russian air safety regulations will allow the use of foreign regulatory frameworks as recommendations. The use of such systems in warning and evacuation management systems latest technologies, as a guiding sound, will be able to ensure the proper level of safety for people in the building.
Connecting an audible siren and a light siren to the Erythea Micra 2M and Erythea Micra 3 alarm systemsSound annunciator(howler for current up to 0.2 A and voltage 12 Volts) and light siren (LED lamp for a current of up to 0.2 A and a voltage of 12 Volts) are connected directly to the alarm device. Let's consider the connection using the example of a light-sound (combined) siren MAYAK-12-KP. The sound and light siren control channels operate independently of each other.
With factory default system settings sounder when an alarm in ZONES 1...4 is processed, it turns on for 1 minute; when the system is armed or disarmed, a short sound signal is issued. RELAY 1 is used in the system to control the sound siren, RELAY 2 to control the light siren. If the system does not provide for the connection of a sound or light alarm, then RELAY 1 and RELAY 2 can be reprogrammed to solve other problems.
Change control settings The sounder can be activated through the configuration program "Erythea Micra 3":
Let's look at the connection diagram for a street siren Ademco 702 to alarm systems Erythea Micra 3 and Erythea Micra 2M. The current consumption of the siren is quite large, so we connect this siren via the built-in alarm RELAY 3 to an external backup battery. When RELAY 3 is triggered (set the response time of relay 3 to 20 seconds so that when turned on, the siren does not completely discharge the battery), the Ademco 702 siren turns on and operates on a backup battery. Connection diagrams:
Go to tab 17 (RELAY 3) and configure the operation of RELAY 3 in the "ROAR" mode (the parameter is circled in red), set the on time (the parameter is circled green) and the number of the zone, when triggered in the "ARMED" mode, the siren will be turned on (the parameter is circled in blue; in this example, the siren will turn on when an alarm occurs in ZONE 1).
Remote installation of sounder control parameters
If necessary, you can remotely adjust the sounder control parameters by sending an SMS message to the device SIM card number in the following format:
#RN=2,p1p0,m1m0-s1s0,d,bip,s
Example. Required to be set remotely following parameters operation of the sound annunciator (howler):
#R1=2.03.01-12.0.1.3
Write the command without spaces as the text of an SMS message on your phone and send the message to the device’s SIM card number.
A light-sound annunciator can become a convenient means of transmitting light and in the event of an emergency emergency situations in buildings of various types and purposes. Light and sound annunciators provide timely signals about the start of evacuation, remaining active throughout the day, operating from a standard power supply.
Various models and modifications of light and sound alarms are actively used to ensure safety on industrial facilities, in retail establishments, entertainment and public areas.
Each device must correspond to the characteristics and purpose of the room in which it is installed. Typically, a suitable light and sound siren is selected based on the noise level in the room. The type of activity of the people who are in it is also taken into account.
Before installing a light and sound alarm, it is necessary to determine the mode in which it should operate. This may be a general, simplified or special mode of operation. Last option Most often used at security posts and in medical institutions, in control rooms, when the fire alarm system is under the control of specially trained personnel.
In standard mode, sirens operate in public, residential and rented premises. To ensure comprehensive security, several devices are mounted on opposite walls, connected to the alarm system and operate from regular network power supply
The light and sound siren (220V) can be connected to the security system either by soldering or by the standard, default screw method. The connection of input and output wires through the siren terminals is carried out by duplicating them.
Operation of the siren in standby mode involves installation, in which communication control is performed by connecting wires to the end element. Typically, such an element is a resistor with a diode. When installing sirens, external connection of diodes is prohibited.
If we talk about operational capabilities and design differences, here we highlight:
Regardless of the type, a device such as a light-sound siren can be installed at objects with fire and security alarms not only to provide light and sound signals during the evacuation of people, but also if necessary to provide certain signals to personnel.
Despite the relatively limited functionality, which is dictated by the purpose of standard sirens, there are currently a sufficient number of various modifications of devices for this purpose. Modified sirens are intended for use in the most innovative integrated security systems and modern fire alarms.
Among the main advantages that distinguish the light-sound combined siren, it is worth highlighting modern design, availability of conditions for installation both outdoors and indoors, as well as the ability to issue sound and light signals simultaneously. This, in turn, becomes extremely important for ensuring safety at facilities with high level noise and smoke in the premises.
The cost of domestically produced light and sound sirens falls in the average price range. The price of the simplest models varies from 70 to 150 rubles. The cost of combined and modified devices can reach 350 rubles, which fully corresponds to their functionality.
Naturally, the same light and sound siren may have different prices depending on pricing policy one or another retail chain. However, for most consumers, the price of domestic and imported devices still remains more than acceptable. Therefore, such security systems are available to a wide range of interested buyers.
If we talk about the most popular models available to domestic consumers, then light and sound devices of the Mayak brand come out on top. Today, such relatively inexpensive, truly reliable, functional and durable systems are widely used in domestic industrial, retail, entertainment, exhibition and public facilities. If necessary, fire alarm systems in residential premises can be equipped with Mayak brand sirens.
"Mayak" alarms do an excellent job of their main task - notifying people about an emergency using signals that can simultaneously affect a person's vision and hearing. Mayak brand devices cope with this task perfectly well, which is confirmed by practice and numerous reviews from specialists.
In the event of an emergency, devices in this category light up with a bright pulsating light, which illuminates a special alarm or direction indicator. The light signal is accompanied by a loud siren, clearly audible in noisy conditions. Currently, such alarms are in demand not only when it comes to ensuring security in enterprises, but also among individuals.
However, when giving preference to light and sound sirens of the Mayak brand, you need to understand that for their effective operation it is necessary to select the right type of device that matches the features of the existing alarm system. It is also necessary to calculate in advance their sufficient quantity, based on the conditions and characteristics of the room. Therefore, you should approach the choice of alarms wisely, preferably relying on the advice and opinions of experienced specialists.
The purpose of this article is to introduce designers, installers and integrators of warning systems, sound systems, and public address systems with the basic principles and features of electroacoustic design. The main attention in this article is paid to the features of the placement of voice alarms (loudspeakers) in closed protected spaces.
One of the main tasks solved in the process of electroacoustic calculation, performed at the initial stage of designing fire warning systems - SOUE, is the task of selecting and placing voice annunciators (hereinafter referred to as loudspeakers). Loudspeakers can be installed both in open areas and in closed (protected) rooms. The purpose of this article is to propose and justify options for the optimal placement of voice alarms (hereinafter referred to as loudspeakers) in closed (protected) rooms.
In enclosed spaces, it is recommended to install indoor loudspeakers, as they are the most optimal in terms of parameters and quality. Depending on the configuration of the room, these can be ceiling or wall types. Proper placement of loudspeakers allows for uniform distribution of sound in the room, hence achieving good intelligibility. If we talk about sound quality, it will be determined mainly by the quality of the selected speakers. So, for example, when using ceiling loudspeakers, it is necessary to take into account that the sound wave from the loudspeaker propagates perpendicular to the floor, therefore, the sounded area at the height of the listeners’ ears is a circle, the radius of which is taken to be equal to the difference between the installation height (mount) of the loudspeaker and the distance to the mark of 1.5 m from the floor (according to regulatory documentation). In most problems for calculating ceiling acoustics, sound waves are identified with geometric rays, while the directivity pattern (DP) of the loudspeaker determines the parameters (angles) of a right triangle; therefore, to calculate the radius of a circle (the leg of the triangle), the Pythagorean theorem is sufficient. To provide even sound throughout a room, speakers should be installed so that the resulting areas touch or slightly overlap each other. In the simplest case, the required number of loudspeakers is obtained from the ratio of the size of the sounded area to the area sounded by one loudspeaker.
One of the main parameters that must be determined in the calculations is the pitch of the speaker chain. It will be determined by the size of the room, the installation height of the loudspeakers and their directional pattern (PDP).
When placing wall-mounted speakers in corridors along one wall, the recommended spacing is:
(Arrangement step, m) = (Corridor width, m) x 2
(Arrangement step, m) = (Corridor width, m) x 4
When arranging wall-mounted speakers in rectangular rooms along two walls in a checkerboard pattern, the placement step is:
When placing back-to-back wall-mounted speakers in rectangular rooms along two walls, the placement step is:
Here is the main requirement of regulatory documentation (ND):
The number of sound and speech (loudspeakers) fire alarms, their placement and power must ensure the sound level in all places of permanent or temporary residence of people in accordance with the norms of this set of rules.
The installation of loudspeakers and other voice annunciators (loudspeakers) in protected premises must exclude concentration and uneven distribution of reflected sound.
Voice annunciators (loudspeakers) must be located in such a way that at any point of the protected object where it is required to notify people about a fire, the intelligibility of the transmitted speech information is ensured.
The design of warning systems is accompanied by an electroacoustic calculation (EAC). The consequence of a competent EAR is optimization - minimizing technical means, increasing the quality of perception. The quality of perception, in turn, is characterized by sound comfort for background music and intelligibility for speech messages. The criterion for the correctness of the EAR is the requirements of regulatory documentation (ND), which can be divided into:
It should be noted that the RD sets out only the necessary (minimum) requirements, while sufficient (maximum) requirements are ensured by the presence of competent techniques, and in their absence, by the literacy and responsibility of the designer.
The following requirements are stated. Sounders must provide a sound pressure level such that:
SOUE sound signals provided general level sound (the sound level of constant noise together with all signals produced by the sirens) is not less than 75 dBA at a distance of 3 m from the siren, but not more than 120 dBA at any point in the protected premises.
This paragraph contains two requirements - the requirement for minimum and maximum sound pressure.
The loudspeaker must provide a (minimum) sound signal level at a distance of 1 m from the geometric center:
Let's define the design point:
Calculation point (PT) is the most critical place of possible (probable) location of people in terms of position and distance from the sound source (loudspeaker). RT is selected on the design plane - an (imaginary) plane drawn parallel to the floor at a height of 1.5 m.
The main requirement for the (necessary) sound signal level is set out in the ND:
Sound signals of the SOUE must provide a sound level of at least 15 dBA above the permissible sound level of constant noise in the protected room. Sound level measurements should be carried out at a distance of 1.5 m from the floor level.
The main requirement for the placement of loudspeakers is set out in the ND:
The installation of loudspeakers and other voice annunciators (loudspeakers) in protected premises must exclude concentration and uneven distribution of reflected sound.
Voice annunciators (loudspeakers) must be located in such a way that at any point of the protected object where it is required to notify people about a fire, the intelligibility of the transmitted speech information is ensured.
According to , the placement of loudspeakers is part of the organizational measures carried out during the design of the SOUE and called electroacoustic calculation. The most relevant is not just the arrangement, but the optimal arrangement of loudspeakers, which allows minimizing the amount of estimated resources (time) and material resources.
The methods of placing loudspeakers are closely related to their design features. The most generalized classification is:
Based on their design, loudspeakers can be divided into internal and external. A characteristic feature of the internal design is the IP protection class. For indoor loudspeakers, IP-41 is sufficient, for external speakers – at least IP-54. For indoor use, primarily for cost-saving purposes, indoor loudspeakers are used.
Depending on the tasks being solved, loudspeakers of different types can be used design. For example, depending on the configuration of the room, ceiling-mounted or wall-mounted speakers can be used. For sounding open areas, horn loudspeakers are used, due to their characteristics, protection class, high degree of sound directionality, and high efficiency.
To carry out proper placement of loudspeakers, we need the following characteristics (basic parameters) of the loudspeaker:
The loudness of a loudspeaker cannot be measured directly, so in practice it is expressed in terms of sound pressure levels, measured in decibels, dB.
The sound pressure of a loudspeaker is determined by both its sensitivity and the electrical power supplied to its input:
Speaker sensitivity P 0, dB (speaker sensitivity is sometimes called SPL from the English SPL - Sound Pressure Level) - sound pressure level measured on the working axis of the loudspeaker, at a distance of 1 m from the working center at a frequency of 1 kHz with a power of 1 W.
There are several main types of power:
Loudspeaker power rating – electric power, at which the nonlinear distortions of the loudspeaker do not exceed the required values.
Loudspeaker rated power– is defined as the highest electrical power at which a loudspeaker can operate satisfactorily for a long time on a real sound signal without thermal and mechanical damage.
Sinusoidal power– maximum sinusoidal power at which the loudspeaker must operate for 1 hour with a real music signal without receiving physical damage (cf. maximum sinusoidal power).
In general, the power setting should be the value specified by the speaker manufacturer.
To calculate the sound pressure level at the design point, it remains to determine one more important parameter– the amount of sound pressure reduction depending on the distance - divergence, P 20, dB. Depending on where the loudspeaker is installed - in interior spaces or in open areas, different formulas (approaches) are used.
Knowing the parameters of the loudspeaker - its sensitivity - P 0, dB, the input sound power P W, W, and the distance to the RT, r, m, we calculate the sound pressure level L 1, dB, developed by it in the RT:
Sound pressure in the RT with simultaneous operation of n loudspeakers:
The effective sound range of a loudspeaker is the distance from the loudspeaker to the point at which sound pressure, does not exceed the value (US+15) dB:
The effective sound range (loudspeaker) D, m, can be calculated:
Let's divide all loudspeakers into three main classes, differing in the direction of emission of sound energy.
Ceiling– loudspeakers, the sound energy of which is directed perpendicular to the design plane (floor) [Sound energy is directed along the working axis of the loudspeaker].
Wall mounted– loudspeakers whose sound energy is parallel to the design plane (floor).
Horn– loudspeakers, the sound energy of which is directed at a certain angle to the design plane (floor).
Under templates We will understand the geometric region, which is the projection of the sound field of the loudspeaker onto the calculation plane:
The loudspeaker is a wideband device. For the lower frequency of the standard range f=200Hz, the loudspeaker can be considered as a sound emitter of a spherical wave. As the frequency increases, the speaker pattern begins to narrow and concentrate inside a spherical cone with an opening angle [the angle between the generatrices of the spherical cone (in English coverage angle)], determined by the value of the spherical cone. This idea does not fully correspond to established practice, according to which the sound field at the output of a loudspeaker is usually approximated by a semi-ellipse. It is shown that for the (average) SDN = 90 0 the quantitative estimates for the cone and ellipse coincide.
Estimation of the effective area voiced by loudspeakers of various types can be associated with the problem of finding the area formed by the intersection of a given spherical cone with the working plane. Let's use the well-known geometric concept, according to which the result of the intersection of a plane and a cone at different angles is various elliptical surfaces - hyperbola, parabola, ellipse and circle, Fig. 1.
Hyperbola is obtained as a result of the intersection of a cone and a plane intersecting one of its generatrices.
Parabola is obtained as a result of the intersection of a cone and a plane parallel to one of its generatrices.
Ellipse is obtained as a result of the intersection of a cone and a plane intersecting both of its generatrices.
Circle is obtained as a result of the intersection of a cone and a plane parallel to its base.
The effective area sounded by a loudspeaker is the area on the working plane within which the sound pressure remains within the limits determined by the loudspeaker's radiation pattern.
Let's calculate the effective areas voiced various types loudspeakers.
The problem of optimal speaker placement can be related to the results obtained in the previous chapter. Let's give a definition:
The placement of loudspeakers must be carried out in such a way that any potential design point necessarily falls within the limits covered by the radiation pattern of the nearest loudspeaker.
In the previous section we got three main geometric figures[Which we will use in the future as tracing paper (figures) to fill (uniformly cover) the surface] - circle, sector and ellipse. The placement problem can be reduced to uniform coverage [Cf. the problem of “tiling” the surface in mathematics] of the entire working plane.
In practice, the placement of loudspeakers is carried out taking into account reflections from surfaces [Taking into account reflections is very relevant. It should be noted that the so-called direct sound (sound energy received by the listener in the first 50 ms) consists of 80% reflected energy (the so-called primary reflections), and the clarity of perception (which, by the way, like intelligibility is not taken into account in the standards) directly depends on the proportion of direct diffusion energy indoors. Within the framework of the elementary EAR (see the previous chapter), it is proposed to take into account no more than one reflection (cf.)].
We will take reflections into account based on the geometric ray theory, in which sound energy is identified with a geometric ray reflected from the surface at the same angle and in the same plane, Fig. 2.
When colliding with a surface, some of the sound energy is lost. The fraction of absorbed sound energy Pabs., dB, can be determined by knowing the absorption coefficient Kabs. of the surface:
When taking reflections into account, it is necessary to check the following boundary condition, Fig. 2:
If condition (8) is met, the placement of loudspeakers can be carried out taking into account reflections.
Most surfaces such as parquet, laminate, wood, concrete practically do not absorb [So, for example, for wood paneling at a frequency of 4 kHz, K abs = 0.11, P abs = 0.5 dB]. In further examples of speaker placement, as a simplification, we will assume that sound energy is completely reflected from the surface.
From Fig. 3 it can be seen that the sound in the RT comes from 2 loudspeakers. Knowing the speed of sound in air v=340m/s and the delay time t=0.05s, it is easy to obtain the critical distance Rcr, m, at which the echo becomes possible: Rcr = vt = 340*0.05=17m, where v – speed of sound propagation in air (340m/s).
From Fig. 3, the stroke difference should be:
Depending on the directionality of the loudspeakers and their SDP, the spacing can be determined geometrically:
We will consider two main types of premises:
By corridors we mean narrow, extended rooms with ratios of length a (m) and width b (m): a/b≥4.
Rooms with a/b ratios
Let's divide the premises into the following groups:
A comment:
To determine the numerical value of the proposed coefficients (b, h), the average value of the effective sound range D (m) was used, which for P db = 95 dB, NS = 60 dB, will be ~ 10 m and SDN = 90 0.
The way speakers are positioned, with or without reflections, is determined by two factors:
We will consider the concepts of “low/high” ceilings in relation to the methods of placing ceiling speakers.
When placing speakers in low ceilings, it is advisable to take into account reflections from the floor. In this case, to determine the numerical value of the speaker spacing, the following criterion is used:
The sound energy emitted by the ceiling loudspeaker must 'reach' the floor and, reflected from it, to the 'design plane'.
When placing loudspeakers on high ceilings, reflections from the floor can be ignored or criterion (8) must be checked.
We will consider the concept of “narrow/wide” corridors in relation to the methods of placing both ceiling and wall loudspeakers. In both cases we will have to take into account reflections from the floor or walls.
To determine the numerical value of the spacing of wall-mounted speakers in the case of taking reflections into account, we will use the following criterion:
The sound energy emitted by a wall-mounted loudspeaker must reach the opposite wall and, reflected from it, to the wall on which the loudspeaker is installed.
When placing loudspeakers in wide corridors, reflections from walls can be ignored or criterion (8) must be checked.
To clarify the meaning of narrow/wide corridors in the case of using ceiling loudspeakers, let's consider the concept of a loudspeaker chain.
Figure 4 shows a wide corridor in which two strings of ceiling speakers are installed.
The number of chains, K c, pcs., will be determined from the ratio:
Let's look at examples of speaker placement for different types premises (cases) and conditions for determining the spacing W, m.
The placement of ceiling speakers in corridors with high ceilings without taking into account reflections [As noted above, due to the height of the ceilings or the presence of reflective surfaces] from the floor should be done in increments, Fig. 5:
When ShDN=90 0, R=h–1.5:
The loudspeaker, taking into account the ShDN, must reach the working plane.
When ShDN=90 0:
The placement of ceiling speakers in corridors with low (less than 4 m) ceilings can be done taking into account reflections (from the floor) in increments, Fig. 6:
The placement of wall-mounted loudspeakers in (wide, over ~3 m) corridors, placed along one wall, without taking into account reflections, should be done with a step of W = 2R:
where ShK is the width of the corridor, Fig. 7.
With ShDN=90°, R=ShK we have Ш=2ШК.
Effective range, for arbitrary long-distance traffic:
For ShDN = 90°:
Let us write down the criterion for determining the effective range, taking into account the installation height of the loudspeaker, H, m. For an arbitrary long-distance beam:
The placement of wall-mounted loudspeakers in (narrow, up to ~3 m) corridors, placed along one wall, taking into account reflections, can be done with a step W = 4R, where R is calculated by formula (16), Fig. 8.
With ShDN=90°, R=ShK we have Sh=4ShK.
The loudspeaker, taking into account the ShDN, must reach the opposite wall twice, taking into account the ShDN.
Effective range, for arbitrary long-distance traffic:
For ShDN = 90°, excluding absorption:
Taking into account the installation height, see formula (18).
It is advisable to arrange wall-mounted speakers in medium-sized rectangular rooms, with the possibility of placing them along two opposite walls, in a checkerboard pattern with a step W = 2R:
where b is the width of the room, Fig. 9.
With ШДН=90°, R= b we have Ш=2b.
The loudspeaker, taking into account the ShDN, should reach the opposite wall.
Effective range, for arbitrary long-distance traffic:
For ShDN = 90°:
Wall-mounted loudspeakers in large rectangular rooms can be placed on opposite walls, in any order, with a step determined by half the distance to the opposite wall, b/2 (m) W=2R.
Where b is the width of the room, Fig. 10.
With ШДН=90°, R= b we have Ш=b.
The loudspeaker, taking into account the ShDN, should penetrate half the distance to the opposite wall, Fig. 10.
Effective range, for arbitrary long-distance traffic:
For ShDN = 90°:
Taking into account the installation height is carried out similarly to formula (18).
The placement of loudspeakers in rooms with complex configurations is carried out as follows. The sounded (designed) room is analyzed, divided into separate sections, for each of which an appropriate arrangement scheme is selected from the above. The main task, in this case, comes down to the optimal joining of individual sections.
Timely information about the outbreak of a fire helps to effectively evacuate people and begin operational measures to eliminate the source of the fire. This is especially true for structures in which a significant number of people live or work. For these purposes, sirens are used.
One type of such equipment is a light-sound alarm, where light and sound are used to transmit an alarm signal. With its help they are equipped fire and security systems responsible for the prompt evacuation of people in the event of a threat to their life.
A light and sound siren is understood as a complex electronic device that sends simultaneously visual and audio signals. alarms. Almost all modern security and fire alarm systems are equipped with such devices, which are responsible for the prompt evacuation of people when the first signs of danger appear.
Sounders are usually installed at the following facilities:
The advantage of light and sound signaling is the use of a duplicated signal to notify about danger. This allows you to attract as much attention as possible when there is heavy smoke, or when the building is very noisy.
Often devices are placed in an explosion-proof housing, which facilitates their uninterrupted operation in fire conditions. There are intrinsically safe models designed for installation in hazardous areas, and conventional devices.
To signal danger, the light and sound siren uses red and yellow light; blue and green colors can also be provided. The light can be either flashing or constant. The sound mode and character of the sound signal may also vary depending on the model of the device.
A modern light and sound siren consists of several modules:
The design of the light and sound alarm is designed in such a way that it can continue to operate in extreme and aggressive influences. To prevent unauthorized opening, the device is equipped with a special access contact. There are special mounting holes and openings for the power and control cables.
Due to the extensive warning coverage area, light and sound equipment is most often mounted on walls and other premises structures. This allows you to achieve the greatest visual and acoustic coverage of the surrounding space.
It is important to do everything possible to ensure that there are no obstacles in the directions of sound waves, and that the human eye can clearly perceive the inscriptions on the scoreboard or light indication in conditions of both natural and artificial lighting.
The specifics of installation of light and sound signaling equipment are influenced by its type, place of application and type of housing.
Wireless devices are more convenient in this regard: their installation involves simply attaching the base, while other parts are located on the board under the cover. If the siren is powered by a cable, then special channels will have to be used to lay it. If the alarm system is installed in street conditions, it is recommended to place the wiring inside corrugated metal pipes. To prevent the operation of the device from being affected by precipitation, protective visors are used.
There is a wide range of light and sound explosion-proof sirens available for sale. Considering the fact that human life directly depends on their work, it is better to give preference to proven models, with optimal ratio price quality. The higher the protective properties of the case, the wider the capabilities of the device, the higher its price, which can reach 8-10 thousand rubles.
The purpose of this combined fire-security device is to notify people of an emerging danger through sound and light signals.
Installation and maintenance activities may only be carried out if you have the appropriate experience.
This light and sound alarm is not intended for use in explosive areas. When carrying out installation, it is important to ensure reliable protection of the equipment from climatic and atmospheric influences.
Mayak-12-KP has a sound pressure of 105 dB. The disadvantage of the device is the inability to change the volume level. In cases where the signal strength is not enough, it can be strengthened using a howler. The material used to make the case is steel. The siren is compact in size and modern design. The equipment may be used in temperature conditions from -30 to +55 degrees.
This siren looks like a sign with the inscription “Exit” on a red or green background. The convenience of this device lies in its ability to not only signal the start of a fire, but also indicate the direction of evacuation. The volume of the sound signal is set at 100 dB.
The collapsible design makes it possible to install any inscription on the display. The body is made of polycarbonate with a transparent insert in front made of acrylic glass.
The functioning of the light and sound siren "Molniya-12-3" is guaranteed at temperatures from -30 to +55 degrees. To simplify installation, the device body is equipped with special holes. This allows for surface mounting on the wall surface. The light source is an LED line that illuminates the display on a three-dimensional scale.
To operate the device, you will need a 12 or 24 V DC source.
For communication with external sources The siren has a special terminal block.
Visual and light warnings can operate in parallel or separately; the operating mode of the device is set depending on the operating conditions.
The Biya brand light and sound annunciator provides an acoustic pressure level of 85 dB, and is capable of continuously sending alarm signals throughout the day.
For power supply, an alternating voltage of 220 V and 50 Hz is used, light signals are sent by a 25 W electric lamp. Sound notification is provided by an electrodynamic circuit that operates at temperatures from -40 to +50 degrees and air humidity up to 98%.
