Handbook for Sound Engineers

Fundamentals of Audio and Acoustics 35

The Occupational Safety and Health Administration
(OSHA) is responsible for assuring that public spaces
remain in compliance regarding sound exposure. Sound
systems are a major source of high level sounds and
should work within OSHA guidelines. Tinnitus, or
ringing in the ears, is one symptom of excessive sound
exposure.

2.10 Monitoring Audio Program Material

The complex nature of the audio waveform necessitates

specialized instrumentation for visual monitoring.

Typical voltmeters are not suitable for anything but the

simplest waveforms, such as sine waves. There are two

aspects of the audio signal that are of interest to the

system operator. The peaks of the program material

Figure 2-17. The equal-loudness contours. Illustration courtesy Syn-Aud-Con.

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Sound Pressure Level—dB ref. 20

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Loudness level

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Figure 2-18. Weighting scales for measuring sound levels.

Illustration courtesy Syn-Aud-Con.

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Relative response—dB Figure 2-19. The time offset between sound arrivals will

determine if the secondary arrival is useful or harmful in

conveying information to the listener. The direction of

arrival is also important and is considered by acousticians

when designing auditoriums. Courtesy Syn-Aud-Con.

Audible Effects of Delayed Signals of Equal Level