Subject: Re: Devices for recording and impulse response measurements: revised version (UNCLASSIFIED) From: Bob Masta <audio@xxxxxxxx> Date: Sat, 3 Nov 2007 09:47:47 -0500 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>Angelique: My Daqarta for Windows software does the basic operations you mention, using a standard Windows sound card (which can be a USB type). It includes an Auto-Calibration facility to calibrate the mixer attenuator steps via a loop-back cable, after which you must perform a single full-scale range calibration on each line or output. That will allow Daqarta to display absolute Volts. If you want to see SPL, you need to supply a frequency response calibration curve for the microphone and/or speaker involved. (A simple text file is OK, or you can measure it with Daqarta.) Sound cards in general don't respond down to DC, and few even go down to 1 Hz. However, if I understand your needs correctly, you are not concerned about continuous 1 Hz tones, but only impulses. In that case, the sound card's coupling capacitors will pass brief waveforms just fine; I don't think you will have any problems there. 145 dB SPL is rather a lot to capture without distortion. I don't recall exact numbers, but I think this will require a small condenser mic, maybe 1/8 inch. (Smaller mics handle higher SPL.) Daqarta can do real-time waveform, spectrum, or spectrogram analysis. It can capture impulses and can perform synchronous waveform averaging to reduce noise. HOWEVER, it does not at this time have a built-in MLS facility. Spectra are limited to 1024 samples (512 lines) but there is a special interpolation option that can read a peak's amplitude and frequency with resolution similar to a 64K FFT. You can supply weighting curves to make specific measurements. (An A-weighting curve is supplied in the package.) You can set the cursor readouts to Sigma mode to read the RMS energy or power (including SPL) between any two frequencies. There is also a large-readout Voltmeter option with a Peak mode, and you can set its dB reference for relative measurements. There is an extensive Help system built in (several hundred pages), and a complete copy in conventional HTML pages is available to browse on the Daqarta site. I'd be glad to answer any specific questions. Best regards, ================================================= On 2 Nov 2007 at 15:13, Scharine, Angelique (Civ,ARL/ wrote: > Classification: UNCLASSIFIED > Caveats: NONE > > I've gotten several very helpful suggestions - but so far, I'm only > clearer on what we need - not necessarily on what to get! I'm hoping > that if I clarify and revise my original request for suggestions, that > some of the suggestions will be nearer to what we need. > > We're looking for a portable system or two portable systems to do the > following tasks: > > 1. Record sounds in the environment, including weaponfire at levels of > approximately 145 dB SPL (peak), and do real-time analysis, including > measurement of various kinds of SPLS. > > 2. Record (binaural) impulse responses, mostly for the creation of > virtual environments, but also for characterization of research > laboratories, etc. > > We have quality microphones, loudspeakers and amps that should suffice > in most cases, although specific considerations and suggestions are > welcome. > > What we are really looking for is a user friendly software package that > does the real-time analysis and recording and an external sound card to > use with a laptop. Ideally, this system could be calibrated so that the > software gives absolute values - but this isn't essential. Our current > system does allow for this. However, when used for recording of very > loud sounds, there seems to be no way to turn the autorange feature off, > which means that the resulting recordings are severely clipped. > > We've gotten some good suggestions for the room acoustics features > described in #2, but I'd like to be sure that we cannot get a single > system that will do both tasks before proceeding. > > Thanks again for the useful suggestions! > Angelique > > They laughed when I said I was going to be a comedian. They're not > laughing now. -Bob Monkhouse, comedian (1928-2003) > > Angelique Scharine PhD > Army Research Lab - HRED > AMSRD-ARL-HR-SD > APG, MD 21005-5425 > > (410) 278-5957 (landline) > 298-5957 (dsn) > (410) 278-3587 (fax) > > Classification: UNCLASSIFIED > Caveats: NONE Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis www.daqarta.com Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!