Ambient Noise Level

by John Bosco
(USA)

Are there noise meters with a range of measurement starting from a low decibel level of approximately 0 dB? How can we determine the noise level in a quiet room in which a crowd is waiting eagerly and silently for a string band to begin a concert?

Thanks for the information about noise meters. It really helped me.

John

Reply from Noise Help:

John,

I'm glad to hear the noise meter information was helpful!

Measuring background (ambient) noise levels gets into the field of acoustics, which is not my area of expertise, but here's what I can tell you.

As you've probably noticed, most sound level meters for personal use or for industrial use are rated for sound levels down to 30 or 40 decibels (dB). There are challenges in measuring noise levels lower than this, including the characteristics of the microphone used, and the noise contributed by the device and by the operator. The sound level meter itself can run at about 7 to 15 dB, and if that is not corrected for, it is impossible for the unit to accurately measure a noise level lower than that.

Several companies make instruments rated for measurements down to 20 dB, including Quest Technologies and Cirrus Research.

Norsonic makes sound level meters accurate down to 10 dB, using specialized microphones.

To accurately measure noise levels down to 0 dB, you need a state-of-the-art sound analyzer, such as made by Norsonic.

Ambient noise levels

are sometimes expressed in NC (Noise Criterion) ratings. Concert halls and recording studios aim for ambient noise level ratings of NC-15 to NC-20; NC-15 is considered the lowest level that is feasible to achieve outside the laboratory.

I hope this gets you started in the right direction! For the best information and advice on measuring low levels of noise (or "quietness") you would want to consult an acoustician.

Regards,
Sarinne