Input sound from microphone into dB indicator

[MelissaM]

Hi,

I wanted to know if it was possible to use the sound coming from a microphone or sonometer into a decibels indicator in Labview.

I have tried to analyse the sound that my microphone was getting but all I was able to do was measure the sound from a amplitude waveform graph and frequency indicator. My goal is to acquire sound from a sonometer and show it in Labview so that I can attach leds to the results.

Thanks in advance!

-Melissa

[Bob_Schor]

A dB scale is a log transformation of a ratio of physical quantities (such as relative waveform amplitude, or relative power).  Look it up on the Web.  You can either (a) transform your data so they are in dB (relative to something) or (b) log-transform the plot.

Bob Schor

[ewang52]

Hi Melissa,

Decibel values can be displayed in LabVIEW. However, the decibel scale is a logarithmic scale that represents a ratio of two values. Usually, one of these is some kind of standard reference level, while the other is power or field-type quantity. To further assist you, we will need to know what kind of values your microphone is outputting to your computer. You can find this information from the user manual of your computer.

Best,

Eric

Applications Engineering

[MelissaM]

Hi there guys,

I dont quite understand what you mean. All I want to do is take the sound coming from the microphone connnected in the input of my computer and see the value of the sound data in decibels. Up until now i have done this but I'm not so sure its right ...

Can you tell me step by step or attach a VI ? It would help me a lot!

Thanks again,

Melissa

[Bob_Schor]

Speaking in terms of sound, the decibel scale gives relative loudness on a logarithmic scale.  0 dB is around the softest sounds humans can hear.  As the sound pressure level grows by a factor of 10, dB increases by 20.  Generally sounds >85 dB are sufficiently loud to damage hearing over time (shorter times for louder sounds).

If you want to express your sound in dB, you need to define what 0 dB is.  You then measure your sound, divide it by the 0 dB level, take the log, multiply by 20, and there's your answer.  Note that 0 dB cannot be zero (otherwise you'd be dividing by zero!).

Bob Schor

[MelissaM]

I understand what dB is but I dont quite understand what you mean by ''measure the sound and devide it by 0 dB level '' how do i do that in labview.

Melissa

[El_Markador]

Hi Melissa,

What Bob is getting at is that you need to find out what magnitude of amplitude your microphone is producing at what you think 0 dB should be. For example, you could just have the microphone pick up the sounds of an empty room, and then use that amplitude value as your 0 dB reference. In your VI, take the values of incoming amplitude, divide the values by the value you defined, take the log, and then multiply that by 20. Now you have your output as dB!

[MelissaM]

Hi,

Thanks a lot I found the solution to my problem !

Melissa

[Yves]

Dear Melissa

I've read your post and hyve a quite similar task. Is it possible to get your solution? This would be great!

Thank you in advance

Yves

[lcornils]

Hi Melissa,

I'm also curious about your solution. It's nice that you found a way. However, can you share it so that other can benefit from it, too?