How do i calculate the bandwidth of a sound?

[mh06069206]

The vi provided will require you to firstly input a sound first. there are more vis but this is the one in question? any known techniques to calculate bandwidth of a sound?

thanks 

[shjukheter]

What exactly you want to know about sound input?

If you want to know the frequency bands of your sound input, apply FFT or pass the sound input to PS and PSD Vi in signal processing palette.

[mh06069206]

thank you for your reply, i have an input signal and i am required to find the bandwidth of the sound, is there any functions on block diagram that calculates this or any techniques I can use to find lowest frequency? i know the highest is 5512 since sampling frequency is 11025. 

[shjukheter]

If you know the frequency range of your input signal, then apply the low pass filter on input sound signal with cutoff frequencies. So, you are expecting see only the lower frequencies and use the cutoff frequencies as your interest of signal.

If you don't know the your lowest frequencies then do the spectral analysis and then cut those lower frequencies. Everything you can get in signal processing palette.

Or try a search on forum as FFT.

[altenbach]

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@mahady wrote:

thank you for your reply, i have an input signal and i am required to find the bandwidth of the sound, is there any functions on block diagram that calculates this or any techniques I can use to find lowest frequency? i know the highest is 5512 since sampling frequency is 11025. 

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I assume you have a certain sound. Your power spectrum will go from DC (0Hz) to 5512Hz, which is the range of possible frequencies, but certainly not the actual bandwidth of your system.

"Bandwidth is the difference between the upper and lower frequencies in a contiguous set of frequencies", so you need to know the actual frequency range of the sound as well as the sensitivity characteristic of all you components, including e.g. the microphone, amplifier characteristics, and any filters. For example if you microphone only works between 1-2KHz, your bandwidth would be only 1KHz, no matter how fast you sample.

Let's assume that you have an ideal lowpass filter at the nyquist frequency and you don't need to worry about alias frequencies.

So, try to input white noise and look at the power spectrum. get the left and right frequency points where the intensity drops to 3dB lower than the  highest peak, take the difference, and you should be almost there. This will give you the bandwidth of your system. The bandwidth of your actual sound might be much less (e.g. if it is the sound of a bird, the lower frquencies might be missing, for example) 😄 Good luck!

[mh06069206]

thank you much appreciated 🙂