Tyco 579-769 Instrukcja Użytkownika

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Fire Alarm
Audio Applications Guide
Guideline for
Designing Emergency
Voice/Alarm
Communications
Systems for Speech
Intelligibility
579-769
Rev. C
© 2005 Tyco Safety Products - Westminster. All rights reserved.
Printed in the U.S.A. All specifications and other information shown were current as of publication, and are subject to change without notice.
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Podsumowanie treści

Strona 1 - Audio Applications Guide

Fire Alarm Audio Applications Guide Guideline for Designing Emergency Voice/Alarm Communications Systems for Speech Intelligibility 579-769 Rev

Strona 2

1-2 Emergency voice/alarm communications systems are used in applications where it is necessary to communicate more detailed information to occupan

Strona 3 - Copyrights and Trademarks

2-1 There are a few fundamental concepts that are necessary to understand when working with emergency voice/alarm communications systems. This cha

Strona 4

2-2 Audio engineers use “Decibels” (dB) to express ratios between levels, such as power, Volts, Amps, and Sound Pressure Levels (SPL). The decibel

Strona 5 - Table of Contents

2-3 When the decibel is used to express SPL, the reference sound pressure is 20 x 10-6 Newtons/m² which is approximately the threshold for hearing

Strona 6

2-4 Sound is created by mechanical vibrations that displace air molecules to create repetitive changes in air pressure. The ear detects these chang

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2-5 The frequency of speech ranges over seven octaves from 125 Hz to 8,000 Hz, with the majority of frequencies contributing to intelligibility fal

Strona 8 - Related Publications

2-6 This section is provided as a summary of room acoustics. See the references in the “Related Documentation” section earlier in this manual for

Strona 9 - Chapter 1

2-7 Several equations are available for estimating the amount of reverberation that can be expected in a room. The equations take into account the

Strona 10 - Intelligibility

2-8 • Increasing the Signal-to-Noise Ratio: Intelligibility degradation from reverberation is essentially a signal-to-noise issue, however when th

Strona 11 - Background Information

2-9 Speakers are essentially “point sources” of sound. Sound radiates outward in all directions, creating a spherical sound pattern. The sound pre

Strona 13 - ()( )( )

2-10 The amount of sound that a speaker can be expected to produce is found in the speaker’s sensitivity rating provided in the manufacturer’s liter

Strona 14 - Sound and Hearing

2-11 The figure below includes a typical polar plot graph and the interpretation of the dispersion angle. 87dB87dBSensitivity = 93dB @10 Feet, 1 W

Strona 15 - The Nature of Speech

2-12 Using the polar information of the speaker, in combination with the distance between the speaker and the listener, you can determine the area t

Strona 16 - Room Acoustics

2-13 Real world speakers have some polar loss at angles less than the rated dispersion angle. In order to determine the actual coverage area for a

Strona 17 - Room Acoustics, Continued

2-14 Once the critical polar angle has been determined, calculate the coverage area for a given speaker-to-listener distance: Coverage Circle Diame

Strona 18

2-15 Speakers used for emergency voice/alarm communication system are wired as “Constant Voltage” systems, where the maximum power output of the amp

Strona 19 - Speaker Basics

2-16 The preceding sections apply primarily to ceiling mounted speakers, generally referred to as “Distributed Overhead Systems.” Another useful m

Strona 20 - Speaker Basics, Continued

2-17 The design of a distributed wall mount system is similar to an overhead system, with some important differences. In a wall mount system the s

Strona 21

2-18 The coverage patterns for a distributed wall mount system are similar to ceiling mount designs, except only a single row is used in the patter

Strona 22

3-1 Intelligibility is a measure of the capability of a message to be comprehended. In simplest terms, it is the reduction of the modulations of sp

Strona 23

Copyright © 2005 Tyco Safety Products – Westminster. All rights reserved. All specifications and other information shown were current as of docu

Strona 24 - Polar Angle

3-2 The figure below lists the relative contributions of each frequency band: Octave Band Contribution to Intelligibility0%5%10%15%20%25%30%35%125

Strona 25

3-3 Background noise causes a reduction in signal-to-noise ratio over all frequencies and modulations. Consider the comparison of the speech signal

Strona 26 - Disadvantages

3-4 Some types of background noise have a greater impact on intelligibility than others depending on the frequency content of the noise. Noise gene

Strona 27 - Mount System

3-5 Distortion of the speech waveform can come from many sources, however it is usually exhibited by an overdriven signal, causing the peaks of the

Strona 28 - Continued

3-6 International Electrotechnical Commission (IEC) 60849 defines intelligibility as: “a measure of the proportion of the content of a speech messa

Strona 29 - Chapter 3

3-7 As described in Chapter 2, speech consists of the frequency of the sound being uttered and the amplitude modulation of that sound into the phon

Strona 30

3-8 Measurement of intelligibility can be complicated, and it sometimes includes subjective analysis. To effectively implement intelligible system

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3-9 Several tools varying in levels of complexity can assist the sound system designer in producing a system of acceptable intelligibility. These r

Strona 33

4-1 An emergency voice/alarm communications system is designed to provide a highly reliable voice reinforcement and distribution network. These sy

Strona 35

4-2 The figure below illustrates a typical emergency voice/alarm communications system: Figure 4-1. Typical Emergency Voice/Alarm Communication

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4-3 A command center should be located at the building entrance and act as a communications center for emergency personnel. The command center is u

Strona 37 - Software

4-4 Speaker circuits convert electrical power from amplifiers into sound. These circuits are wired in a daisy-chain fashion, with a single path of

Strona 38

5-1 The governing specifications for the US Fire Alarm Market are found in the installation standard, NFPA 72® “National Fire Alarm Code.” The fir

Strona 39 - Chapter 4

5-2 For emergency messages to be heard, NFPA 72 suggests that the sound level of the emergency evacuation tone to be measured at 5-feet. This is th

Strona 40 - Communications

5-3 To meet the 15 dBA requirement, there are cases where high levels of background noise require extremely high levels of emergency annunciation t

Strona 41 - Transponder

5-4 Intelligibility has historically been a difficult parameter to measure. Unlike SPL that can easily be measured with a relatively common dBA met

Strona 42

5-5 There is significant explanatory information in Annex A, recently revised for the 2002 edition: From NFPA 72, 2002 Edition: A.7.4.1.4. The desi

Strona 44 - Audibility

6-1 This chapter covers a design methodology that can be used to design a speaker system for an emergency voice/alarm communications system. The a

Strona 45 - Audibility, Continued

iii Chapter 1 Speech Intelligibility Overview 1-1 Introduction ...

Strona 46

6-2 The steps below summarize the speaker system design method. Use these steps in conjunction with the Tyco Safety Products iTool (described late

Strona 47 - Intelligibility, Continued

6-3 Use the following recommendations to maximize system intelligibility: • Ensure at least an 8 dBA signal-to-noise ratio with regard to the spee

Strona 48

6-4 The following examples illustrate the design methodology outlined earlier in this chapter. For these examples, computer based modeling was emp

Strona 49 - Speaker System Design Method

6-5 Click the “Speaker Location” tab on the iTool for more detailed information. The following screen shows a speaker location guide for the offic

Strona 50 - Speaker Design Method

6-6 In this example, consider a standard office corridor with the following specifications: • Dimensions = 100’ L x 12’ W x10’ H • Flooring

Strona 51 - Maximizing

6-7 Click the “Speaker Location” button on the iTool for more detailed information. The following screen shows a speaker location guide for the cor

Strona 52 - Applying the Methods

6-8 Gymnasiums are notoriously bad acoustic environments. Extremely high reverberation times can be expected because of the large room volume plus

Strona 53

6-9 Click the “Speaker Location” button on the iTool for more detailed information. The following screen shows a speaker location guide for the gy

Strona 54

6-10 During an intelligibility survey in an office building, an employee lobby area measured 0.60 CIS intelligibility, failing the NFPA suggested 0.

Strona 55

6-11 The existing design had two wall mounted speakers, to the left and right of the entrance doors. Figure 6-15. Lobby Layout The following scr

Strona 56

ivInfluences on Intelligibility... 3-2 Introduction ...

Strona 57

6-12 The following screen shows the reverberation time and speaker coverage information: Figure 6-18. Lobby Reverberation Time and Speaker Cove

Strona 58

6-13 Designing Emergency Voice/Alarm Communications Systems for Speech Intelligibility requires awareness of the area dimensions, anticipated backg

Strona 60

7-1 This chapter contains a glossary of technical terms that are used throughout this manual. Refer to the page number listed in this table for in

Strona 61 - Conclusion

7-2 This list provides brief descriptions of various terms relating to this publication: ABSORPTION COEFFICIENT – The ratio of absorbed-to-reflected

Strona 62

7-3 DISTORTION – The undesired change in the waveform of a signal that can lead to diminished clarity in reception or reproduction. ECHO – The repe

Strona 64 - Glossary

IN-1 % %ALcons, 3-7 A acoustical treatment, 2-7 acoustics, 2-6 AHJ, 7-2 Amplifiers, 4-3 audibility, 5-2, 7-2 audio riser interface modules, 4-3 B ba

Strona 65 - Glossary, Continued

IN-2speaker dispersion angle, 2-10 Speaker layout patterns, 2-15 speaker placement, 2-7 speaker, sensitivity, 2-10 speech pattern, 3-4 speech patter

Strona 67

vStep 1: Room Characteristics... 6-2 Step 2: Calculate the Number o

Strona 68

7-1 579-769 Rev. C Printed in the U.S.A. Specifications and other information shown were curre

Strona 69

vi Refer to the publications and web sites listed below for more information regarding sound, speech, and audio intelligibility: • Acoustics – Th

Strona 70 - 579-769

1-1 INTELLIGIBILITY – The capability of being understood or comprehended. In simple terms, intelligibility is an evaluation of changes that occur t

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