Low Noise Microphone

[ctris]

Anyone, come across with low noise microphone. Our company is looking for a low noise microphone. We are intended to use it in our semi anachoic chamber to measure hard disk motor sound power levels from 20Hz to 20kHz.

what does low noise microphone mean and whats the difference between low noise microphone compare to normal free field microphone.

 

[GregLocock]

Microphones generate a certain amount of electrical noise themselves. This prevents them measuring below a certain threshold. I am sure Bruel and Kjaer sell a suitable device.

Firstly, do you want a mic cartridge, preamp, and amp setup, or do you want an integrated sound level meter? Hopefully the latter as that is easier.

Go and have a look at the spec page for the 2236

http://www.bksv.com/pdf/Bp1535.pdf

the quitest tone it will measure is roughly 10 dB, and the noise floor is at 18-20 dBA for overall levels. typically you want at least 10 dB of dynamic range, ie your signal would want to be 30 dBA or so (which is very quiet).

This might be good enough for your purposes. You can hire B&K gear from many places if you want to test it out.

There are many other makes of instrumentation, I am most familiar with B&K. I don't acually like their current range of sound level meters very much, I find them awkward and confusing to use, but the technical specs and support for B&K are superb.

Cheers

Greg Locock

 

[okdb]

Hi,

Here's another god sound level meters manufacturer:
www. norsonic.no
They are technically very strong and very keen to help.

Another possiblity is a computer based system like the one form 01dB

http://www.01db-stell.com/GB/products/fiche_produits_noise2.asp?produit_select=22&groupe=6

If you just need to measure the sound levels, a standard sound level meter will do. If you however need to do some research and improvement on you product, I think that you need a meter that can give you FFT-analysis as well.

For very low noise levels, it is possible to combine 2 microphones in order to reduce the electrical noise. We had one day to measure background noise in an anechoic room and we manage to measure -16dB at 1kHz!

Regards,
OKdB

 

[ingacus]

you need measure power you must see in Larson Davies company in EEUU. you need a sound level meters or sonometers for power measuring this must be type I sound level meter for power measuring.

this must meet with ISO for this kind o measurement.

marioa@sinruido.com
ing acoustics

 

[pheon]

You may have some confusion between two characteristics of microphones.

1. All microphones have a sound level below which they cannot measure due to the electrical noise that is inherent in their components.

2. Some microphones are designed to be used in an acoustically noisy environment (e.g. outside broadcasting) and have directionality, that is they reject noise coming from directions other than the speaker.

You probably want a microphone with low noise in the first sense. Buy or rent a B&K or similar instrument microphone and associated amplifier and you should be OK.