×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Isotropic noise generation

Isotropic noise generation

Isotropic noise generation

(OP)
Anyone know how or have experience with generating isotropic noise?  I've used normally distributed noise but I can't seem to turn up any material on isotropic.  Thanks.

RE: Isotropic noise generation

Amusingly, the very first hit is now this exact thread.

(...Looks skyward, waves at passing Google robot...)

RE: Isotropic noise generation

Put the search term in quotes to exclude misses and the ONLY hit is this exact thread.

As we all probably already know, isotropic means equal in all directions. Perhaps the OP could provide more details of the application. Is it related to acoustical measurements?  

RE: Isotropic noise generation

I'm guessing he means EM radiation, so I'd start with an EM interference testing suite. Might help if he defined what he really meant by isotropic, it has several meanings.

Cheers

Greg Locock

I rarely exceed 1.79 x 10^12 furlongs per fortnight

RE: Isotropic noise generation

(OP)
Sorry about not providing some more background.  Yes this is in regards to acoustics and I'm looking at the behaviour of some system composed of hydrophones when stimulated with isotropic versus normally distributed noise.

RE: Isotropic noise generation

Isotropic in this case must mean that the noise is arriving from all directions. Tricky.

 

RE: Isotropic noise generation

I think you had better give a proper explanation of what you want, your use of the phrase "normally distributed" worries me.

Assuming VE1BLL is right then isotropic noise is easily generated on land, in a reverberant room.


 

Cheers

Greg Locock

I rarely exceed 1.79 x 10^12 furlongs per fortnight

RE: Isotropic noise generation

He's testing hydrophones. So must be in a big tank of water.

Relying on reflections to fill the test space with noise may affect the spectrum of the noise.

I was also wondering about the use of that phrase.   

RE: Isotropic noise generation

(OP)
Currently I simulate the noise applied at the elements (hydrophones) of the array as normally distributed noise with a mean of zero and standard deviation of 1.  For example in matlab if I have 10 elements (hydrophones) with a sampling rate of 1K the data coming from the array would be

time_data = randn(10, 1024); % 1 second of data assuming Fs is 1K

This looks like it is going in the right direction:
http://books.google.com/books?id=YIXRVNAaBdUC&lpg=PA24&ots=0NDKgLNbxb&dq=isotropic%20noise%20generation&pg=PA24#v=onepage&q=&f=false

I'm trying to do this for noise that is now an isotropic field instead of a 1-D field.

Thanks again.

RE: Isotropic noise generation

you need to model each sound source and then work out the contribution of each source at each hydrophone, allowing for attenuation with distance, and cancellation or reinforcement from the other sources.

Might have been a bit quicker getting to here from there if you had explained you were only simulating the whole experiment.



 

Cheers

Greg Locock

I rarely exceed 1.79 x 10^12 furlongs per fortnight

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources