Tyco 579-769 - Manual

v Step 1: Room Characteristics ................................................................................ 6-2 Step 2: Calculate the Number of Speakers ........................................................... 6-2 Step 3: Audio Power and Individual Speaker Wattage Tap ...........................

1-1 INTELLIGIBILITY – The capability of being understood or comprehended. In simple terms, intelligibility is an evaluation of changes that occur to speech that impact comprehension. More specifically, intelligibility is concerned with evaluating reductions of the modulations of speech that cause un...

2-1 There are a few fundamental concepts that are necessary to understand when working with emergency voice/alarm communications systems. This chapter introduces basic concepts of sound, but is not intended to be an exhaustive treatment of the subject. Note: Refer to the “Related Documentation” sect...

2-2 Audio engineers use “Decibels” (dB) to express ratios between levels, such as power, Volts, Amps, and Sound Pressure Levels (SPL). The decibel is not an absolute measure like Volts and Amps, rather it is used to make comparisons between two numbers. The decibel is defined as the logarithm of two...

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 for a normal listener. When using a dB meter to measure sound, the meter is performing the calculation between the received SPL and the reference SPL: ⎟...

2-4 Sound is created by mechanical vibrations that displace air molecules to create repetitive changes in air pressure. The ear detects these changes in air pressure, with the magnitude of the pressure perceived as loudness and the frequency of the changes perceived as pitch. Due to the physiology o...

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 falling between 500 Hz and 4,000 Hz. The creation of “phonemes,” or the sounds that make up words is created by amplitude modulation of those frequencies. A...

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 a list of publications containing more thorough discussions of this subject. Reverberation is one of the most important contributors to reduced intelligib...

2-8 • Increasing the Signal-to-Noise Ratio: Intelligibility degradation from reverberation is essentially a signal-to-noise issue, however when the noise is specifically caused by reverberation it is referred to as the “Direct-to-Reverberant” ratio. Increasing the direct sound field at the listener ...

2-9 Speakers are essentially “point sources” of sound. Sound radiates outward in all directions, creating a spherical sound pattern. The sound pressure is spread over an increasingly larger surface area as the sound moves away from the source. This causes a drop in loudness per unit area. The drop i...

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 literature. “Sensitivity” is the amount of sound (SPL) produced by the speaker with a known signal frequency, power level and distance from the speaker. For ...

2-11 The figure below includes a typical polar plot graph and the interpretation of the dispersion angle. 87dB 87dB Sensitivity = 93dB @10 Feet, 1 W Simplex 4902-9721 Ceiling Mount Speaker Polar Plot - 2kHz 0 º 6dB/division 75 º off axis Dispersion Angle Figure 2-4. Speaker Polar Plot Interpretation...

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 that a speaker can cover. The “Coverage Area” is defined as the plane where the SPL at the edge of the plane drops 6 dB below the on-axis SPL, as illustr...

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 particular speaker, the “Critical Polar Angle” for the speaker must be found. The critical polar angle is the angle where the sum of the distance loss an...

2-14 Once the critical polar angle has been determined, calculate the coverage area for a given speaker-to-listener distance: Coverage Circle Diameter = 2 D 2 tan ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ 2 θ Coverage Area = π 2 2 2 θ tan D ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ Where D 2 is the distance from the speaker to the listener and ...

2-15 Speakers used for emergency voice/alarm communication system are wired as “Constant Voltage” systems, where the maximum power output of the amplifier is obtained at a certain speaker voltage, such as 25 V or 70.7 V. The power output of a speaker, and thus the resulting SPL is controlled by watt...

2-16 The preceding sections apply primarily to ceiling mounted speakers, generally referred to as “Distributed Overhead Systems.” Another useful mounting strategy is the “Distributed Wall Mount System.” Under this configuration, the speakers are placed on walls or columns, and are aimed into the roo...

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 speaker-to-listener distance depends on the listener location in the room. Therefore the audibility calculations must be done with the listener at the fart...

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 pattern. Because of the typically larger potential speaker-to-listener distance, only edge-to-edge and tighter spacing patterns should be used to provide adequ...

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 speech that reduce speech intelligibility. The modulation reductions can also be thought of as a reduction in the signal (the speech) to noise ratio. Not a...

3-2 The figure below lists the relative contributions of each frequency band: Octave Band Contribution to Intelligibility 0% 5% 10% 15% 20% 25% 30% 35% 125 250 500 1000 2000 4000 8000 Frequency component of speech Re la tiv e Contribution to inte lligibility Figure 3-1. Frequency of Speech Contribut...

3-3 Background noise causes a reduction in signal-to-noise ratio over all frequencies and modulations. Consider the comparison of the speech signal below with and without added noise: No Noise With Added Noise Figure 3-2. The Speech Pattern “An Emergency Has Been Reported” with Added Noise Creating ...

3-6 International Electrotechnical Commission (IEC) 60849 defines intelligibility as: “a measure of the proportion of the content of a speech message that can be correctly understood.” Because “understanding” involves evaluation by a human, intelligibility is by definition difficult to quantify abso...

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 phonemes that create words. The STI (Speech Transmission Index) method measures the modulation transfer function for 14 modulation frequency bands spaced at ...

3-8 Measurement of intelligibility can be complicated, and it sometimes includes subjective analysis. To effectively implement intelligible systems in real buildings requires that a simple, accurate, and repeatable method of measuring intelligibility must be available. Fortunately, there are instrum...

3-9 Several tools varying in levels of complexity can assist the sound system designer in producing a system of acceptable intelligibility. These range from simple layout guides for speaker placement to complex computer modeling tools which can accurately simulate and predict sound system performanc...

4-1 An emergency voice/alarm communications system is designed to provide a highly reliable voice reinforcement and distribution network. These systems must deliver messages to building occupants for evacuation in an organized and safe manner. The system can deliver recorded messages automatically b...

4-2 The figure below illustrates a typical emergency voice/alarm communications system: Figure 4-1. Typical Emergency Voice/Alarm Communications System While an emergency voice/alarm communications system is similar to a non-emergency paging system, there are certain features that make emergency sys...

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 used to display the system status and control the annunciation system. This area typically includes the equipment required to generate and distribute mess...

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 electrical continuity from the NAC to the last speaker in the circuit. The speaker circuits can be wired in Class A or Class B configurations. Class A op...

5-1 The governing specifications for the US Fire Alarm Market are found in the installation standard, NFPA 72 ® “National Fire Alarm Code.” The fire alarm audio system is defined within the class of “Notification Appliances.” NFPA 72 defines, among other things, requirements for audibility and intel...

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 ability to design an emergency voice/alarm communications system which is highly intelligible at a reasonable cost, represents a significant advantage to t...

6-2 The steps below summarize the speaker system design method. Use these steps in conjunction with the Tyco Safety Products iTool (described later in this chapter). Determine if the room requires advanced design methods. Some characteristics of a difficult location/space include: • High Background ...

6-3 Use the following recommendations to maximize system intelligibility: • Ensure at least an 8 dBA signal-to-noise ratio with regard to the speech signal. Note: This can result in a higher than 15 dB signal-to-noise ratio for notification tones. If the notification tones become too loud for a part...

6-4 The following examples illustrate the design methodology outlined earlier in this chapter. For these examples, computer based modeling was employed using Tyco Safety Products “iTool” to demonstrate intelligibility. Note: See the iTool Installation and User’s Guide (579-772) for iTool installatio...

6-5 Click the “Speaker Location” tab on the iTool for more detailed information. The following screen shows a speaker location guide for the office space: Figure 6-2. Office Space Speaker Location Guide SPL distribution information, reverberation time results, and speaker coverage information are al...

6-7 Click the “Speaker Location” button on the iTool for more detailed information. The following screen shows a speaker location guide for the corridor: Figure 6-6. Corridor Speaker Location Guide SPL distribution information, reverberation time results, and speaker coverage information are also av...

6-9 Click the “Speaker Location” button on the iTool for more detailed information. The following screen shows a speaker location guide for the gymnasium: Figure 6-10. Gymnasium Speaker Location Guide SPL distribution information, reverberation time results, and speaker coverage information are also...

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 screens below show the lobby speaker location guide and the SPL distribution for the lobby: Continued on next page Applying the Methods, Continued Example 4: L...

6-13 Designing Emergency Voice/Alarm Communications Systems for Speech Intelligibility requires awareness of the area dimensions, anticipated background noise level; wall, ceiling, and floor materials; anticipated occupancy, and any other characteristics that may influence the desired acoustical pro...

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 information on a specific topic. Topic See Page # Glossary 7-2 Chapter 7 Glossary of Terms Introduction In this Chapter

7-2 This list provides brief descriptions of various terms relating to this publication: ABSORPTION COEFFICIENT – The ratio of absorbed-to-reflected sound. The absorption coefficient has a range of 0 to 1. “A” WEIGHTED DECIBEL – The ear is less sensitive to low frequency pitch at low volume levels, ...

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 background noise, 3-3, 5-3 C Ceiling height, 2-14 CIS, 3-6, 7-2 clipping, 7-2 combination system, 7-2 command center, 4-3, 7-2 Common Intelligibility Scal...