measuring sound in db using fft

[karper1986]

measuring db

Hi friends,

I want to measure sound with using FFT, can anyone tell me from what to start. Any ideas?
Any links will be helpful. Thanks.

Best regards,
Karper

 

[doraemon]

fft sound

Hello!

I don't think FFT is the simplest way to measure sound. What would the
FFT be used for? Or tell us what exactly you want to measure.
Do you want to measure the intensity? The pitch?
For intensity, it would be better to calculate the rms power of the signal.
For pitch, FFT will not give you accurate results.

Dora.

Hi friends,

I want to measure sound with using FFT, can anyone tell me from what to start. Any ideas?
Any links will be helpful. Thanks.

Best regards,
Karper

 

[karper1986]

decibels from fft

Hi,

I just want to see some examples or literature about measuring sound, vibration, noise using fft.
If someone have, please give any links, it will be helpful. Thanks.

Best regards,
Karper

 

[doraemon]

mesuring sound

Hello!

What I meant is that FFT has basically nothing to do with measurement.
Usually you measure some kind of sequence of data, and then you process
it. You can use its time representation (the ADC output) and you can also
calculate its frequency representation using FFT if you want to know what
the frequency distribution is, and take some subsequent action based on
the distribution.

So you cannot measure sound using FFT, you can just process your
measurements with FFT.

You may want to try Audacity, a multiplatform program that can display an FFT
of the signal you have recorded. It may giveyou usefule hints about what
you can do.

Dora

Hi,

I just want to see some examples or literature about measuring sound, vibration, noise using fft.
If someone have, please give any links, it will be helpful. Thanks.

Best regards,
Karper

 

[karper1986]

audio to decibel fft

Hello Dora,

Thanks for your fast reply. I think about something like this:
a device that measures the loudness of sound for different frequencies. This device is divided in three
parts: a microphone that captures the sound, one A/D converter that samples
the sound and one FPGA which analyse the data using an FFT algorithm.
LEDs connected to the FPGA are used to indicate different output levels. A
db(A) filter is applied that weights each frequency, before the different output
levels are measured for each frequency.
Or something like this, maybe for captuaring vibration (for example from electrogenerator ect.).
I dont know from what to start, and have not so good imagine how it all works. Sorry for previous messages, maybe not so understanding.
Maybe someone can help me in that. Thanks.

Best regards,
Karper.

 

[FvM]

fft db

Basically as fast µP, e.g. a dsPIC can perform audio spectrum analysis in realtime. FPGA would be necessary when you're targetting to the 100 kHz and MHz domain. See e.g.:

A search a edaboard with the keywords "audio spectrum" or "audio spectrum analyzer" will bring up many interesting contributions. "A" weighting is usually applied in sound level measurement, but not in spectrum analysis.

 

[doraemon]

fft sound db

Hello!

OK, I get it more or less.
So you are thinking about the following:

Measure/Capture -> FFT -> Display

You may want to look at the following **broken link removed**. Full source code is provided.
But I didn't try it, I simply searched for "sound frequency analysis" which is
always a good way to start.

Dora.

Hello Dora,

Thanks for your fast reply. I think about something like this:
a device that measures the loudness of sound for different frequencies. This device is divided in three
parts: a microphone that captures the sound, one A/D converter that samples
the sound and one FPGA which analyse the data using an FFT algorithm.
LEDs connected to the FPGA are used to indicate different output levels. A
db(A) filter is applied that weights each frequency, before the different output
levels are measured for each frequency.
Or something like this, maybe for captuaring vibration (for example from electrogenerator ect.).
I dont know from what to start, and have not so good imagine how it all works. Sorry for previous messages, maybe not so understanding.
Maybe someone can help me in that. Thanks.

Best regards,
Karper.

 

[karper1986]

measuring db sound

Hello Dora and FvM,

Thanks a lot for Your help, it was so helpful. Can you tell me more about sound level measurment or some examples.

Best regards,
Karper.