Labview spectral measurements help

[gavler4321]

I am having trouble understanding spectral measurements. As far i know,i have a raw data input of Voltage to time from 2 microphones and it performs FFTs so that the X-axis is in the frequency domain. However, i am very confused as to what the Y-axis represents and its units. I have been told various things that the Y-axis is SPL in decibels and PSD in Pa/Hz or dB/Hz. I am just generally confused about the Y-axis. I also have an amplifier of gain 100mV/Pa and i am struggling to see how i can incorporate this in calculations. I am trying to achieve a graph of SPL (dB) to Frequency or PSD (dB/Hz) to frequency. What is on my Y-axis when i have Magnitude(Peak) as my selected measurement and dB as my result? What is on my Y-axis when i have Power Spectral Density as my selected measurement and dB as my result? Here is my VI. https://i.imgur.com/J4GOoMm.png

Thanks

[RavensFan]

Attach your image to your message, don't post pictures on 3rd party websites.  Many of us won't trust them.

And if you want to attach a VI, then attach the actual VI file.  A picture of a VI is not the same as a VI.

If you acquire in Volts, then the Y-axis is going to be in volts.  Though the Y axis of an FFT might be volts, or a unit of power or something like that depending on the exact version of FFT you are using.

If you want to convert to Pa and you have 100 mV/Pa, then divide the incoming signal by 0.1 to get the signal in Pascal.

[gavler4321]

Thanks so much for your reply!

Can you tell me what would be on my Y-axis if i had the selected measure as Peak magnitude and the result as dB? Do these settings not matter and the y-axis be Voltage regardless? And the difference between the selected measurement being Peak measurement and power spectral density as from the data i have collected, there seems to be little to no difference in the plots. 

Thanks for your time.

[gavler4321]

Hello

I have a raw signal input of voltage to time from 2 microphones which i am feeding through the spectral measurements express VI. The selected measurement is Peak Magnitude with the result set as dB. I am confused as to what the y-axis of the graph represents as i have been told different things. I have beem told that it is sound pressure level in dB amd that it is still voltage. Can someone clarify what the Y-axis represents and the units?

thanks

[gavler4321]

Hello

Can anyone tell me what i am plotting? I think it is Power in dB but i am unsure. I have a raw signal of voltage/time run through the spectral measurements VI, performing FFTs to put it in the frequency domain but i am unsure of the what is on the y-axis and the units. I have the selected measurement as peak magnitude and the result as dB.

Thanks

[gavler4321]

Hello

Can anyone tell me what i am plotting? I think it is Power in dB but i am unsure. I have a raw signal of voltage/time run through the spectral measurements VI, performing FFTs to put it in the frequency domain but i am unsure of the what is on the y-axis and the units. I have the selected measurement as peak magnitude and the result as dB.

Thanks

[RavensFan]

Yes it is dB.

No need to keep posting the same questions multiple times.  It is Sunday, so the response time on the forums is slower than it would be during the week.