The NEBB Professional 2024 - Quarter 2

Practices to be Aware of in Sound Measurement and Instrument Set-Up

By Stuart McGregor

It’s not uncommon for members of the Sound and Vibration (S&V) Committee to field questions from NEBB S&V Firms and Certified Professionals (CPs) regarding sound data, vibration data, and instrumen tation. Such questions have involved three recurring themes, which we aim to shed light on as a means of helping others avoid the same potential mistakes, use less data, and repeat work: a. The proper instrumentation setting to take sound data to generate Noise Criteria/Room Criteria curves. b. Instrumentation set-up for vibration measure ments, so usable data can be taken. c. The issue of Sound level meter calibration requirements. Those who have taken the Sound CP or Sound CT courses know that the instructors stress the proper setting on a sound level meter when taking sound data to generate Noise Criteria (NC) and Room Criteria (RC) curves/ratings. Remember, most sound specifi cations call for one or two measurements: the overall sound levels which is typically a dBA measurement, and/or the NC/RC rating which is an octave band measurement. The octave band measurement for NC/

RC must always have the instrument set to the fre quency weighting of unweighted or dBZ. In accordance with the 2015 NEBB Sound and Vibration Procedural Standard, a sound level meter/ analyzer should be set up as follows: • Frequency Weighting – Z, Linear, Flat (this designa tion is different for different instruments) • Time Constant – Slow The labeling for the unweighted setting may vary from manufacturer to manufacturer, and may be dBZ, dB(- Flat), or dB(Linear). Read the owner's manual of your instrument. This doesn't seem too hard, however, it brings up a nuance depending on the manufactur er of the sound level meter, or SLM. Let’s look at two examples: • Manufacturer A has set-up options which apply the frequency weighting (dBA, dBC or dBZ) to both the overall sound level and the octave band sound levels. • Manufacturer B has set-up options which allow the user to set the overall sound level frequen • Averaging – time average over 60-seconds • Full Octave data – from 31.5 to 8,000 Hz

The NEBB Professional | Quarter 2 | 2024

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