Software for frequency analysis

[David Pinnegar]

Hi!

Is anyone aware of any software providing a swept frequency sine wave with corresponding amplitude recording facility? This would normally be used in analysing speaker frequency responses of speakers but is also helpful in analysing resonant modes of buildings . . .

Many thanks

David P

[dragonser]

Hi,
I'm sure there are other solutions but I wonder if anyone has used the program Audacity to play back a swept tone and then record the results back from the room ?
Audacity is a sound editing program but if you have a wav [ or mp3 ] file of a swept tone then it should be able to play this back.
of course you might be able to use a Cd player and play back a test track from a CD.
then record the results on a stand alone recorder
there seems to be more info at http://www.acousticsciences.com/matt.htm

looking forward to other replies

regards Peter B

[KB7DQH]

I can think of a number of (and have) programs that will either generate or measure/display, but not do both simultaneously, but then I have not REALLY been scouring the "freeware" as carefully as I should...

I  Also have AF signal generators of one flavor or another and corresponding measurement equipment from a valve-type reccurrent-sweep oscilloscope, voltmeters, a piece of multiplex test equipment (essentially an ELF/VLF/MF radio receiver, called a frequency-selective level meter:)
a "modern" dual-trace "o" scope...  and a "consumer-grade" SPL meter... all of which when combined with audio frequency recording equipment could produce workable results but with lots of boxes to set up, cook in, calibrate, etc.
before one could begin making measurements... Yes, something that one could load up onto a notebook computer, plug in a reasonable reference microphone and appropriate speaker/amplifier combination, then hit the "go" button... would certainly "make life easier"... 

Eric
KB7DQH

[revtonynewnham]

Hi

There are a few CD's around with various audio test tones - Canford audio do one - and there was/(is?) a bversion with a simple analyzer built into the case.  I've got some software links on another computer - David - drop me an e-mail reminder and I'll try and have a look tomorrow.

I too have used an audio sweep generator - but don't currently have access to one.

I thing the "Sound on Sound" magazine has some info - and some downloadable bass test trones (IIRC steps rather than a sweep) - I've got that on another machine as well.

Every Blessing

Tony

[dragonser]

Hi,
I checked and Canford audio do have several different Cd s with test tones on.
I think that Audacity can record and play back at the same time if the sound card on your computer will support that. But I would probably use a test cd and then record the results using Audacity and then try to analyse them.
I think I have the test Cd that was made by Alan Parsons, [ bought at one of the trade shows in the 1990's and I think Alan Parsons himself may have been on the stand ! ].
this seems to be the one that is also available with the audio analyser as an option.
see
<http://www.canford.co.uk/Products/25-245_SOUNDCHECK-2-TEST-AND-DEMONSTRATION-CD-Alan-Parsons-with-SPL-meter-spectrum-analyser>

regards Peter B

[KB7DQH]

Audacity on this machine won't record its own test signals :(

However it shouldn't be too difficult to record the white noise onto a suitable device and play that back for a source signal and then use Audacity or some other program to do the analysis, for example Spectran...  That would be a step in the right direction I would think :-\

Eric
KB7DQH

[Colin Pykett]

Unless the building is very 'dry', swept tones are not very practical.  One would have to sweep them extremely slowly so that at each frequency of interest the impulse response of the building had died away.  Wideband noise is what acousticians usually use for buildings.

But one also has to take into account the frequency response of the speaker as well, because if you don't know the characteristics of your input signal (from the speaker) you can't make much sense of what comes out the other end (i.e. from the building itself at the mic position).  And also the phase response vs frequency of the speaker is required in some cases, e.g. if you want to measure the complex (i.e. a complex number in maths, which captures both phase and amplitude info) impulse response of the building to insert it into an effects processor (convolver).

It's not an easy subject either in theory or practice, which is partly why artificial reverb from FX processors is so often unsatisfactory.  So I'm afraid this is my first and last post on this one -  I don't want to get involved in a competition to see who can have the last word!!

Colin Pykett

[David Pinnegar]

Dear Eric

Thanks for pointing me in the direction of Spectran - when I tried it, although it gave a nice display I couldn't see a way to get it to display a nice scale from 20-20k . . . I've used a pink noise source but the results are very variable in the instant and resulting displays rather coarse . . .

Best wishes

David P

[revtonynewnham]

Hi David

I don't know if this is of use - I haven't got time to look properly today:-

http://www.audiotester.de/

Also, Martin at EOCS offered a CD of various freeware programmes - again, I don't know what's on it - I've not had time (or need) to look so far, but it might be worth dropping him an e-mail.

Good luck

Every Blessing

Tony

[KB7DQH]

Leave it to the Italians ;D

A FREE program (and small enough it only took me 10 minutes to download and install :) 8) 8) 8) :o

And it will generate and analyze simultaneously 8) 8) 8)

http://www.sillanumsoft.org/

Have Fun! ;D

I already have... ;)

Eric
KB7DQH