Any device to measure sound frequency below 20 Hz?

[oem7110]

Does anyone have any suggestions on what device can measure sound frequency below 20 Hz?
Thanks in advance for any suggestions

 

[f95toli]

How sensitive does it need to be?
What about an accelerometer?
I "built" one using a single IC a few weeks ago, there are single ICs out there that only require a +5V supply and will give you a buffered voltage out that is proportional to the acceleration. Very easy to use.

(all I did was to solder 3 wires to the chip, and then I glued the whole thing to the top of a screw to make it stable and easier to attach to things)

 

[oem7110]

How sensitive does it need to be?
What about an accelerometer?
I "built" one using a single IC a few weeks ago, there are single ICs out there that only require a +5V supply and will give you a buffered voltage out that is proportional to the acceleration. Very easy to use.

(all I did was to solder 3 wires to the chip, and then I glued the whole thing to the top of a screw to make it stable and easier to attach to things)

Sensitive is around 1-2 Hz buffer range.
I also need to display the frequency in Hz, could you please give me any suggestions on what kind of IC I need and device to display the Hz in number? where can I purchase it online?
Thanks in advance for any suggestions

 

[f95toli]

I used an Analod Devices ADW22035Z

http://www.analog.com/en/mems-sensors/low-g-accelerometers/adxl103/products/product.html

This will give you a signal out, but it will just be the waveform (although that will of course be true for a microphone as well). Note that an accelerometer measures vibrations , i.e. you need to bolt it to something that is vibrating.

If you want the frequency you need some signal processing as well, either you can but something (expensive) or build it (complicated unless you are good at DSP).
Alternatively, you could connect the accelerometer to a computer using a DAQ (about £100) or even the line-in input of a soundcard if you happen to have a card with a frequency response below 20 Hz; and the do the signal processing using software.

 

[oem7110]

This will give you a signal out, but it will just be the waveform (although that will of course be true for a microphone as well). Note that an accelerometer measures vibrations , i.e. you need to bolt it to something that is vibrating.

I want to measure sound frequency, and cannot bolt device into object that is vibrating.
Do you have any suggestions what device I should use and can purchase it available on market?
Thanks you very much for any suggestions

 

[skeptic2]

Have you tried an electret microphone, or an array of electret microphones? You may need to use larger coupling capacitors and a higher gain amplifier, but I don't see why it wouldn't work.

 

[sophiecentaur]

For a good solution to this problem it would be good to know a few more details - like what range of frequencies is involved and what level of sound. You say you haven't anything to 'bolt something to" but you could very easily make a tuned cavity (box with a hole in - or an old sub-woofer, cannibalised) that could couple your sound to a microphone, making it very sensitive to the low frequency. Tuning would not be of such benefit if you need to measure more than a narrow frequency range (unless you could trim it each time).