Calculation of the voice warning system: formulas, theoretical calculations, calculation example. Calculation of the sound pressure level at a distance

Li2 = Li1 - 20 Lg r
where:
Li2 – sound pressure level at the tested point, dB;
Li1 is the level of sound pressure generated by an acoustic emitter at a distance of 1 m, dB;
r is the distance from the emitter to the tested point, m.

Li3 = Li2 - Liр
Li3 = Li1 - 20 Lg r - Liр
where:
Li3 is the sound pressure level at the test point, taking into account intermediate partitions with a door, dB;
Liр – signal attenuation in the presence of intermediate partitions with a door, dB;
It is necessary to take into account intermediate partitions with a door (signal attenuation Lip is about 5 dB - in the premises of production workshops and 10 dB - in the premises of administrative buildings) located between the emitter and the test point. The maximum distance from the emitter to the point being checked, taking into account the intermediate partition with a door (1st - in production workshops, 2nd - in administrative buildings) is about 10 m. , with a sound pressure level at a distance of 1 m - not less than 100 dB.

Li3 \u003d 100 - 20 Lg 10 - 5 \u003d 75 dB (in the premises of production workshops)

Li3 \u003d 100 - 20 Lg 10 - 20 \u003d 60 dB (in the premises of administrative buildings)

At the points of the checked premises, the most remote from sound annunciators, the sound pressure level complies with the requirements of SP3. 13130.2009. In other rooms, the distance from the siren to the most remote points (including intermediate partitions with a door) is less than the values ​​used in the calculations. The results of calculations of sound pressure levels at different distances from sound annunciators in the premises of production workshops and premises of administrative buildings (the value is given in brackets) are shown in Table 2.

Table 2.

Calculation number
Li1, dB Distance r, m Signal attenuation 20 Lg r, dB
Lop, dB
LN, dB Level
sound pressure
Li2, dB
1 100 1 0 60(45) 75(60) 100
2 100 2 6,02 60(45) 75(60) 93,98
3 100 4 12,04 60(45) 75(60) 87,96
4 100 6 15,56 60(45) 75(60) 84,44
5 100 7 16,90 60(45) 75(60) 83,10
6 100 8 18,06 60(45) 75(60) 81,4
7 100 10 20 60(45) 75(60) 80
8 100 15 23,52 60(45) 75(60) 76,48
9 100 17 24,61 60(45) 75(60) 75,35

The requirement of clause 4.2 of SP3. 13130.2009 is carried out at a distance of no more than 10 m from the emitter of the sound annunciator, taking into account intermediate partitions with a door in the premises of production workshops (one partition) and administrative buildings (two partitions), respectively.

Good day.

We have already said that the requirements for SOUE (warning and evacuation control systems) are regulated by volume SP 3.13130.2009. "Set of rules. Fire protection systems. Fire warning and evacuation control system. Requirements fire safety».

The main requirement for sound systems is that they must provide a minimum sound pressure level at a level of 1.5 m from the floor (i.e. at the height of the ears of an average person) 15 dB above the average noise level in the room, but not less than 75 dB. At the same time, the maximum sound pressure level created by the SOUE should not exceed 120 dB: this is a pain threshold, then it’s still useless - only harm can be done. Therefore, if the noise level at the facility is, say, 110 dB, then your SOUE should squeal no quieter or louder than 120 dB, and an increase in efficiency should be achieved due to any lighting effects - strobe lights for example. In bedrooms, hotels, hospital rooms, etc. The sound level is measured at the height of a sleeping person's head.

There are many options for placing sound sources. You can attach a horn loudspeaker of the “bell” type of nightmarish power in the corner of the hall and let it yell “for the whole forest”. As a result, at the far end of the room, the sound will satisfy the requirements, and people will deafen near the sound source. So I forgot to add: the "Code of Rules" also requires a uniform distribution of sound (clause 4.7. Installation of loudspeakers and other voice annunciators in protected premises should exclude concentration and uneven distribution of reflected sound.).

Therefore, in large rooms, ceiling speakers are widely used - they allow you to create exactly the same uniform distribution of sound pressure. There are many designs for installation in dropped ceilings, there are suspended speakers that look like chandeliers.

In corridors and small rooms, wall-mounted speakers are quite suitable, their placement is strictly regulated: not less than 2.3 m from the floor, but not less than 15 cm from the ceiling. By the way, there are bidirectional loudspeakers: in the middle of the corridor, he attached it to the wall, he speaks back and forth.

It should be added that, in order to avoid large power losses on the wires, the amplifiers produce a high-voltage signal, 100-120 V. The speakers are equipped with step-down transformers.

About the calculation of the SOUE with ceiling speakers:

The number of ceiling speakers for scoring a room is calculated without taking into account power - pure geometry. We believe that the speaker pattern is 90 degrees, it is necessary that they sound evenly, without overlapping, in rooms at a height of 1.5 m from the floor. Those who wish can draw, I'm too lazy, so without any details:

b we take the height of the room minus 1.5 m, proudly call the resulting number "h". We hang the speakers from each other at a distance of 2h, from the wall - h.

The area covered by one in-ceiling speaker is approximately:

Now we take the area of ​​\u200b\u200bthe room and divide by this very S (op), we get the number of speakers. For example, we have a hefty warehouse of 7000 sq.m, height 6m. In this case h=6m-1.5m=4.5m. S (op) turns out to be approximately 2x4.5x2x4.5 \u003d 81 square meters. m. Number of speakers:

N=7000:81=86

Now about power. Any normal speaker (loudspeaker) in the number specifications has such an interesting parameter as sensitivity, measured in W/m. True, later, for the convenience of calculations, this is translated into dB, those who wish can themselves look for how to convert watts to decibels, this is already a theory, I don’t want to delve into details. In short, sensitivity is the sound pressure that a speaker creates at a distance of 1 m with a power dissipated on it of 1 watt.

We have to create a sound pressure greater by 15 dB than the noise level in the room. In order not to run with a sound level meter, we will use a table of typical noise levels in rooms:

Since we have a warehouse, we take a noise level of 70 dB. Take the LPA-6 speaker from Louis Plus, it has a sensitivity of 94 dB, i.e. at a power of 1 W at a distance of 1 m from it, it creates sound pressure = 94 dB. We need to get the sound pressure at a distance of 4.5 m (our distance "h")

70dB+15dB = 85dB

Let's use the sound pressure attenuation graph c depending on the distance from the speaker, provided by the same Louis-Plus company:

At a distance of 1 m, attenuation = 0, and at the distance we need 4.5 m it is about 13 dB. Those. from the original 94 dB (speaker sensitivity or sound pressure at a distance of 1 m), we need to subtract 13 dB. We get that at a power of 1 W, our speaker will swing us at a level of 1.5 m from the floor with a pressure of 81 dB. And you need 85 dB.

Let's look at the characteristics of our speaker:

Look, in the column "Inclusion power" There are 3 connection options: 6 W, 3 W and 1.5 W. Those. there are several taps on its matching transformer, allowing, at a voltage of 100 V on the transformer, to develop a power of 6 W, 3 W or 1.5 W.

And, for complete happiness, one more plate - gain in dB depending on the power dissipated on the speaker:

We need to swing 85 dB at a distance "h" from the speaker. We got the estimated 81 dB, i.e. add 4 db. We look - at a power of 3 W, the sound pressure amplification will be 4.8 dB, which means we connect the speaker at a power of 3 W, we will have 85 dB with some margin.

We multiply the speaker power by their number and get the minimum sufficient power of the amplifier. In our case, this is 3W x 86 = 258W.

All in all, pretty confusing at first, but let's recap.

1. Without being tied to any power, stupidly based on geometry, we consider the area that one speaker should sound at a given room height. Then, based on the area of ​​the room, we count the number of speakers.
2. We select a speaker and, based on its sensitivity, we consider what sound pressure it can create at a height of 1.5 m from the floor at a power of 1 W
3. And finally, we consider how much power we need to develop on the speaker in order to get the sound pressure we need at that very magical height of 1.5 m. Naturally, if this power is higher than the maximum power of the speaker, we will have to choose another model.

Well, in general, and all the horrors. From the second approach, it's not so scary.

And here is the very first formula:

I recommend to remember by heart, the benefit is simple. Imagine you are inspecting an object, the customer asks how much the notification will cost. With this formula, you can count on your fingers the number of ceiling speakers and plus or minus bast shoes, adding the cost of amplifiers and cables to them, at least indicate the scale of prices. The customer likes this efficiency.

Questions - in the comments or by mail [email protected], the newsletter subscription form is below.

In accordance with the regulations that entered into force in 2003. new fire safety standards, the design is required to provide specified sound levels. There is a reference in the document to a method for measuring sound level, but no reference to how to correctly calculate the required number and power of loudspeakers.

Let's try to describe the procedure for calculating the notification in steps.

1. It is necessary to determine the number of speakers to ensure even sound distribution.

• horn..................................................30-45 about
• searchlight ...............................30-45 about
• wall-mounted.................................................75-90 about
• ceiling .................................................80-90 about

Also, according to installation experience, we can assume that it is allowed to place ceiling speakers through a distance equal to the height of the ceiling (in this case, the sound uniformity will turn out to be rather mediocre, but it will satisfy the airbag standards. If uniform sound is required, then you will have to install through "ceiling height - human height "). Wall speakers are installed at a distance equal to the width of the corridor (room). And horn and floodlights are arranged so that crowded places fall into the radiation pattern. When installing wall and horn loudspeakers, it is necessary to follow the rule that if you want to install several loudspeakers in the same area, it is better to install them in the center and point them in different directions than to put them on the walls and point them towards the center. Legibility and quality in the latter case will be much worse.

2. Determine the noise level in the room. To do this, you can measure it or use a table with approximate levels, for various types premises.

3. The broadcast level must exceed the noise level by:

• for background music..................................at 5-6dB
• for emergency notification .................... at 7-10dB.
• for high-quality music .............................. at 15-20dB

4. To take into account the attenuation of the sound level from distance (within the radiation pattern), you can use the table:

5. To take into account the increase in sound level depending on the input power, you can use the table:

6. To calculate the sound pressure level at the required distance, you can use the simplified formula:

SPL (dB) = SPL nameplate - SPL attenuation + SPL increase

SPL (db) - level at the required distance in the radiation pattern

SPL passport - sound pressure level according to the passport at a distance of 1 m (dB / W / m)

SPL attenuation - attenuation level depending on the distance (see table)

SPL increase - - level of increase depending on the input power (see table)

From the above formula, you can easily calculate the required power for a single loudspeaker. By summing the power of the speakers, you can calculate the total power of the amplifier. The power of the amplifier is recommended to be selected with a 20% power margin. When operating the system, you will be able to verify this.

For example: there is a retail space measuring 20x30m with a ceiling height of 3m. It is required to sound it with background music, but taking into account the possibility of emergency notification.

For uniform sounding, 20:3-1 = 5 rows of 30:3-1 = 9 pieces will be required. total 45 pcs.

The sound level at a distance of 1.5 m from the loudspeaker (ceiling height - the height of the shortest person) must be at least 63 + 7 = 70 dB. Therefore, if you use ART-01 (Inter-M) loudspeakers with a power of 1 W, (according to the passport, the sound pressure level at a distance of 1 m is 90 dB.), the formula will take the form:

SPL (Sound Pressure Level) = 90-3+0 =87 dB. Which is more than 70. So that these speakers are suitable for sounding this room. And in principle, if only an emergency notification is needed, then the number can be even less (you can count it yourself).

If you do not want to bother yourself with "complicated" mathematical calculations, then you can always use any program for calculating the number of loudspeakers, for example, from TOA. When using equipment from other manufacturers, it is necessary to take into account the difference in their sound pressure from the selected type. You can download the program for calculating warning systems (8,2mb)

They are the most important component of fire protection systems. In the process of designing warning systems, an electro-acoustic calculation is performed. The basis for electroacoustic calculation is a set of rules developed in accordance with article 84 federal law FZ-123 SP 3.13130.2009 dated July 22, 2008 This article is based on the following main points of the set of rules.

• 4.1. The sound signals of the SOUE should provide a total sound level (the sound level of constant noise together with all signals produced by annunciators) of at least 75 dBA at a distance of 3 m from the annunciator, but not more than 120 dBA at any point of the protected premises
• 4.2. Sound signals of the SOUE should provide a sound level of at least 15 dBA above the permissible sound level of constant noise in the protected room. Sound level measurement should be carried out at a distance of 1.5 m from the floor level
• 4.7. Installation of loudspeakers and other voice annunciators in the protected premises should exclude the concentration and uneven distribution of the reflected sound
• 4.8. The number of sound and speech fire alarms, their placement and power must ensure the sound level in all places of permanent or temporary stay of people in accordance with the norms of this set of rules

The meaning of the electro-acoustic calculation is reduced to determining the sound pressure level at the calculated points - in places of permanent or temporary (probable) stay of people and comparing this level with the recommended (normative) values.

In the sounded room there is a different kind of noise. Depending on the purpose and features of the room, as well as the time of day, the noise level varies. The most important parameter in the calculation is the value of the average noise. Noise can be measured, but it is more correct and convenient to take it from ready-made noise tables:

In order to hear sound or speech information, it must be 3 dB louder than the noise, i.e. 2 times. The value 2 is called the sound pressure margin. In real conditions, the noise changes, so for a clear perception useful information against the background of noise, the pressure margin should be at least 4 times - 6 dB, according to the standards - 15 dB.

Satisfaction of the conditions set forth in clauses 4.6, 4.7 of the set of rules is achieved by organizational measures - the correct placement of loudspeakers, preliminary calculation:

• loudspeaker sound pressure,
• sound pressure at the calculated point,
• effective area sounded by one loudspeaker,
• the total number of loudspeakers needed to sound a certain area.

The criterion for the correctness of the electroacoustic calculation is the fulfillment of the following conditions:

1. The sound pressure of the selected loudspeaker must be "at least 75 dBA at a distance of 3 m from the siren", which corresponds to a loudspeaker sound pressure value of at least 85 dB.
2. Sound pressure at the design point d.b. above the average noise level in the room by 15dB.
3. For ceiling speakers, the installation height (ceiling height) must be taken into account.

If all 3 conditions are met, the electroacoustic calculation is completed, if not, then the following options are possible:

• choose a loudspeaker with greater sensitivity (sound pressure, dB),
• choose a loudspeaker with more power (W),
• increase the number of speakers
• change the speaker layout.

2. Input parameters for calculation

Input parameters for calculations are taken from terms of reference(TOR) (provided by the customer) and technical specifications for the designed equipment. The list and number of parameters may vary depending on the situation. Sample input data is shown below.

Speaker options:

• SPL
• Pgr– loudspeaker power, W,
• SDN– Beam width, deg.

Room options:

• N– Noise level in the room, dB,
• H– Ceiling height, m,
• a– Room length, m,
• b– Room width, m,
• Sp– Room area, m2.

Additional information:

• ZD– Sound pressure margin, dB
• r– Distance from loudspeaker to calculated point.

Sounded room area:

Sp \u003d a * b

3. Loudspeaker sound pressure calculation

Knowing the rated power of the loudspeaker (PW) and its sensitivity SPL (SPL from the English Sound Pressure Level - the sound pressure level of the loudspeaker measured at a power of 1W, at a distance of 1m), it is possible to calculate the sound pressure of the loudspeaker developed at a distance of 1m from the emitter.

• SPL– loudspeaker sensitivity, dB,
• rvt- loudspeaker power, W.

The second term in (1) is called the "power doubling" rule or the "three decibel" rule. The physical interpretation of this rule is that for each doubling of the source power, its sound pressure level increases by 3dB. This dependence can be represented tabularly and graphically (see Fig. 1).

Fig.1. Sound pressure versus power

4. Calculation of sound pressure

To calculate the sound pressure at the critical (calculated) point, it is necessary:

1. Select calculated point
2. Estimate the distance from the loudspeaker to the calculated point
3. Calculate the sound pressure level at the calculated point

As a calculated point, we choose the place of possible (probable) location of people, the most critical in terms of position or distance. The distance from the loudspeaker to the calculated point (r) can be calculated or measured with an instrument (range finder).

Calculate the dependence of sound pressure on distance:

• r– distance from the loudspeaker to the calculated point, m;
• 1

ATTENTION: formula (2) is valid for r > 1.

Dependence (2) is called the “inverse square” rule or the “six decibel” rule. The physical interpretation of this rule is that for each doubling of the distance from the source, the sound level decreases by 6dB. This dependence can be represented tabularly and graphically, Fig. 2:

Fig.2. Sound pressure versus distance

Sound pressure level at the design point:

• N- Noise level in the room, dB (N from English Noise - noise),
• ZD– Sound pressure margin, dB.

At AP=15dB:

If the sound pressure at the calculated point is higher than the average noise level in the room by 15 dB, the calculation is correct.

5. Effective range calculation

The effective sound range (L) is the distance from the sound source (loudspeaker) to the geometric location of the calculated points located within the limits of the SRP, the sound pressure in which remains within (N + 15dB). In technical slang, "the distance that the loudspeaker penetrates."

In English literature, the effective acoustical distance (EAD) is the distance at which speech clarity and intelligibility is maintained (1).

Calculate the difference between the sound pressure of the loudspeaker, the noise level and the pressure margin.

• p- the difference between the sound pressure of the loudspeaker, the noise level and the pressure margin, dB.
• 1 - coefficient taking into account that the sensitivity of the loudspeaker is measured at 1 m.

6. Calculation of the area sounded by one loudspeaker

The basis for estimating the size of the sounded area is the following setting:

The calculation will be based on the following assumptions: The radiation pattern (radiation) of a loudspeaker can be represented as a cone (sound field concentrated in a cone) with a solid angle at the top of the cone equal to the width of the radiation pattern.

The area sounded by the loudspeaker is the projection of the sound field limited by the opening angle onto a plane drawn parallel to the floor at a height of 1.5 m. By analogy with the effective range: The effective area sounded by the loudspeaker is the sound pressure area within which does not exceed the value of N + 15dB (form 5).

NOTE: The loudspeaker radiates in all directions, but we will rely on input data - sound pressure levels within the radiation pattern. The correctness of this approach is confirmed by statistical theory.

Let's break the loudspeakers into 3 classes (types):

1. ceiling,
2. wall,
3. horn.

8. Calculation of the effective area sounded by the wall loudspeaker

9. Calculation of the effective area sounded by a horn loudspeaker

10. Calculation of the number of loudspeakers required to sound a certain area

Having calculated the effective area sounded by one loudspeaker, knowing the total dimensions of the sounded territory, we calculate the total number of loudspeakers:

• Sp– sounded area, m2,
• Sgr– effective area sounded by one loudspeaker, m2,
• int is the result of rounding to an integer value.

11. Electro-acoustic calculator

The overall result obtained in the form of a flowchart:

Fig.6. Block diagram of an electroacoustic calculator

Programming example

This calculator (written in Microsoft Excel) implements an elementary short method - the electroacoustic calculation algorithm described above. This program can be downloaded from our website.

Fig.7. Electroacoustic Calculator in Microsoft Excel

Based on the developed calculation algorithm, the ON-LINE electro-acoustic calculator on our website also works.

APPENDIX 1. List and brief characteristics of ROXTON loudspeakers

One of the main tasks to be solved in the process of electro-acoustic calculation performed at the initial stage of designing fire warning systems - SOUE is the task of selecting and arranging voice annunciators (hereinafter referred to as loudspeakers). Loudspeakers can be installed both in open areas and in closed (protected) premises. The purpose of this article is to propose and justify options for the optimal placement of voice annunciators (hereinafter referred to as loudspeakers) in closed (protected) premises.

In enclosed spaces, it is recommended to install internal loudspeakers, as 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 you to ensure even distribution of sound in the room, therefore, to achieve 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 must be taken into account that the sound wave from the loudspeaker propagates perpendicular to the floor; m from the floor (according to regulatory documentation). In most tasks for calculating ceiling acoustics, sound waves are identified with geometric rays, while the radiation pattern (DN) of the loudspeaker determines the parameters (angles) of a right-angled triangle, therefore, to calculate the radius of a circle (leg of a triangle), the Pythagorean theorem is sufficient. For uniform sounding of the room, the loudspeakers 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 sounded area to the area sounded by one loudspeaker.

One of the main parameters that needs to be determined in the calculations is the Loudspeaker Chain Spacing. It will be determined by the size of the room, the height of the loudspeakers and their directivity pattern (SPD).

When arranging wall-mounted loudspeakers in corridors along one wall, the recommended spacing is:

excluding reflections from walls:

(Spread spacing, m) = (Corridor width, m) x 2

• taking into account reflections from the walls:

  (Spread spacing, m) = (Corridor width, m) x 4

When placing the wall speakers in rectangular rooms on two walls in a checkerboard pattern, the arrangement step:

When placing wall-mounted loudspeakers in a rectangular room on two walls, the spacing step is:

Primary requirements

Here is the main requirement of regulatory documentation (ND):

The number of sound and speech (loudspeakers) fire alarms, their arrangement and power must ensure the sound level in all places of permanent or temporary stay of people in accordance with the norms of this set of rules.

The design of warning systems is accompanied by the performance of an electro-acoustic calculation (EA). The consequence of a competent EAR is optimization - minimization technical means, improving 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 (RD), which can be conditionally divided into:

• requirements for a voice annunciator (loudspeaker);

  requirements for the levels of sound signals;

  requirements for the placement of voice annunciators (loudspeakers).

It should be noted that the RD sets out only the necessary (minimum) requirements, while sufficient (maximum) requirements are provided by the presence of competent methods, and in their absence, by the literacy and responsibility of the designer.

Speaker Requirements

The following requirements are set out. Sounders must provide a sound pressure level such that:

The sound signals of the SOUE provided a total sound level (the sound level of constant noise together with all the signals produced by the annunciators) of at least 75 dBA at a distance of 3 m from the annunciator, but not more than 120 dBA at any point of the protected premises.

This paragraph contains two requirements - the requirement for minimum and maximum sound pressure.

Minimum sound pressure

The loudspeaker must provide a (minimum) sound level at a distance of 1 m from the geometric center:

Maximum sound pressure

Let's give the definition of the calculated point:

Design point (PT) - the place of possible (probable) location of people is the most critical in terms of position and distance from the sound source (loudspeaker). RT is selected on the calculated plane - (imaginary) plane, drawn parallel to the floor at a height of 1.5 m.

Requirement for audio signal levels

The basic requirement for the (necessary) sound signal level is set out in the RD:

Sound signals of the SOUE should provide a sound level of at least 15 dBA above the permissible sound level of constant noise in the protected room. Sound level measurement should be carried out at a distance of 1.5 m from the floor level.

Placement Requirements

The main requirement for the placement of loudspeakers is set out in the RD:

Installation of loudspeakers and other voice annunciators (loudspeakers) in protected premises should exclude concentration and uneven distribution of reflected sound.

Voice annunciators (loudspeakers) should be located in such a way that at any point of the protected object where it is required to alert people about a fire, the intelligibility of the transmitted speech information is ensured.

Taking into account the basic characteristics of loudspeakers

According to, the placement of loudspeakers is part of the organizational measures performed in the design of the SOUE and called electroacoustic calculation. The most relevant is not just the placement, but the optimal placement of loudspeakers, which allows minimizing the amount of calculated resources (time) and material resources.

Ways of arranging loudspeakers are closely related to their design features. The most generalized is the following classification:

by execution;

by design features;

by characteristics;

according to the method of matching with the amplifier.

Accounting for the type and design features of loudspeakers

By design, loudspeakers can be divided into internal and external. characteristic feature internal execution is IP protection class. For internal loudspeakers, IP-41 is sufficient, for external loudspeakers - not lower than IP-54. For premises, primarily for the sake of economy, internal loudspeakers are used.

Depending on the tasks to be solved, loudspeakers of various designs can be used. So, for example, depending on the configuration of the room, ceiling-mounted or wall-mounted loudspeakers can be used. For scoring open areas, horn loudspeakers are used, thanks to their characteristics, the protection class, high degree directivity of sound, high efficiency.

The specifics of accounting for the main parameters of loudspeakers

To implement a competent placement of loudspeakers, we need following characteristics(basic parameters) loudspeaker:

Loudspeaker Sound Pressure Calculation

Loudspeaker loudness 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 both by its sensitivity and by the electrical power supplied to its input:

Loudspeaker sensitivity P 0, dB (loudspeaker sensitivity is sometimes called SPL from English. SPL - Sound Pressure Level) - the 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 at a power of 1 W.

Loudspeaker power

There are several main types of power:

Loudspeaker Rated Power- electric power at which the nonlinear distortion of the loudspeaker does not exceed the required values.

Loudspeaker power rating- is defined as the highest electrical power at which the loudspeaker can work satisfactorily for a long time on a real sound signal without thermal and mechanical damage.

Sinusoidal power is the maximum sinusoidal power at which the loudspeaker must operate for 1 hour with a real music signal without suffering physical damage (cf. maximum sinusoidal power).

In general, the value specified by the loudspeaker manufacturer should be used as the power parameter.

The sound pressure of the loudspeaker is recommended to be calculated depending on the turn-on power of the loudspeaker.

Basic calculations

Sound pressure reduction with distance

To calculate the sound pressure level at the calculated point, it remains to determine one more important parameter - the magnitude of the decrease in sound pressure depending on the distance - divergence, P 20 , dB. Depending on where the loudspeaker is installed - indoors or outdoors, different formulas (approaches) are used.

Calculation of sound pressure level in RT

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:

Effective Range Calculation

The effective sound range of the loudspeaker is the distance from the loudspeaker to the point at which the sound pressure does not exceed the value (LN+15) dB:

Effective sound range (loudspeaker) D, m, can be calculated: