Tone detection WITH time information??????

Question

Hello everybody,
I record continiously sound with my soundcard(10000 Samples at 44100Samples/s.) In this waveform data I try to find 8.5ms sends long 12kHz pulses and the time when they occur.
 I'm using the single tone information VI which enables me to detect the 12kHz pulses. But I need to know when the pulse exactly occurs. Unfortuanetely the VI doesn't output this information although it gets the timing information(time of the 1st sample and sample rate) of the waveform data from the sound input read VI.
I need to determine the time when the pulse occurs in the order of an accuracy of a couple of ms up to 20ms.
What can I do to make the VI to give the time information or is there a better VI(s) you can recommend?
Thank you very much,
Martin
additonal infos:
LABVIEW 8..2.1
notebook dell latiude d630
internal standard sound card
Message Edited by LabviewHans on 07-18-2007 04:53 PM

Answer 1

Hi Lynn,
unfortunately I cannot record output and input signal due to the given hardware.
But I found out that there stopping the sound input vi for sending a ping and starting the sound input vi right afterwards should be ok in terms of hardly missing milliseconds. But I still don't know how can I determine the index of the first amplitude after sending a ping. (If you use Sound input stop VI the data aquisition is stopped immediately, for example at the 3432nd sample out of 10000 samples, and after starting the data aquistion the 3433rd sample would be the first sample after the sending the ping. The problem is that I have no clue how to determine the index(in the example 3433) of the first amplitude value after sending the ping.)
I tried a couple of things to realize that. Here are the two most promising trys:
I checked the sound input vi and I found something like nCumulativeSamplesRead, which sounds very promising, but just shows a value which is a multiple of the number of samples(10000, 20000, 30000 and so on. (reminder:sound input configure is configured for 10000samples at 44100Hz)
Another solution could be the following one: I click at the Send Ping button and I give the sound input vi as much time as it needs to get all 10000 samples. When the VI got its 10000samples the while loop would go into the next interation to get the next 10000samples. But exactly at that point I want to stop the sound input vi. Then I would send the ping. Right afterwards I would start the sound input vi and I would miss hardly milliseconds AND the first value in my array corresponds to the (almost) first amplitude value after sending the ping. This would enable me to determine the distance with an accuracy of a few m, which is sufficient.
But I really need your help at that point because I tried a lot to force the sound input VI to get 10000samples before stopping it, but nothing worked. Do you know how to realize that in Labview?
I created a little test VI...
Thank very much,
Martin
Message Edited by LabviewHans on 07-26-2007 02:38 PM
Attachments:
whenToStop.vi ‏55 KB