dBA Messung mit Soundkarte/ dBA measuring with a sound card

[Alesis]

Hello Coq Rouge,

First i wanna thank you for your help!!!

In the vi now I've left out the window function. That's ok now.

Sombody told me, that i must add up the rated spectrum over the frequency to become an dBA-value (e.g. 120dBA ) and that goes to smaller and smaller increments over an integration.

And he said, i shouldn't use the power spectrum. I should use the normal spectrum...

That's why i use the Express VI!!!

The dBA-value then should be showed in a numeric display.

I hope the explanation is better now   (I don't know how to explain it better at the moment and with my command of English )

The problem in short form: i need a positive dBA-value between 0 and e.g. 170dBA. And i've got no idea how i can realize it 

Unfortunately, I am now a little desperate and depressed...

Best regards

Alesis

Message Edited by Alesis on 11-05-2009 06:36 AM

[Alesis]

I've got an vi without the express vi but with a normal spectrum

[Alesis]

Is there really nobody out there who can help me on my final way?

[Alesis]

Can i add up the rated spectrum over the frequency an make an integration (to become the dBA-value ) like this??? (look at the picture )

Thanks, Alesis

[Coq_Rouge]

Hi first of all. As mentioned before without proper calibration it is outermost futile to do what you do. And for calibration you need professional sound measurements equipment. Now you do some measurement. But they are most certain horrible off-scale. So requesting any values is pointless. I hope I have made my self clear enough.

For summation of the A weighted spectrum I think it will be correct to consider each frequency bin as a single sound source. So for the total sum, you must sum the frequency bins in the proper way.

As an example

If there are two uncorrelated sound sources in a room - for example a radio producing an average sound level of 62.0 dB, and a television producing a sound level of 73.0 dB. Then the total decibel sound level is a logarithmic sum i.e. 

Combined sound level = 10 x lg ( 10^(62/10) + 10^(73/10) ) = 73.3 dB.

You seam to be total lost, and in full panic. An engineer must be able to navigate in unknown water, and digest new information from all available sources. Also you must have some person you can discuss with like a teacher or a professor. I am sure this person is more than willing to help you and push you in the correct direction. But this is not the same as present the complete solution to you assignment. So my advice to you is. Get your act together. Unless you show some professional development I can and will not give you any more help

[Alesis · Accepted solution]

ok thanks anyway for the help.

The area of acoustics and labview are completely new to me.

I can teach me in such a short time-just not as complex topic itself.

The topic itself, I have fully understood. I just do not know how I can do it with labview!

Since the language is completely new for me, I've got not the information that a professional Labview programmers has!

And I would certainly not the complete solution of my project, as this is only a small part of the whole!

But it is the last part and the hardest for me because I have nothing to do with this issue until now and I have no idea how I can do something like this in Labview?

despite everything again thanks for the help ...