Subject:
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Re: NXT sound sensor characteristics
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Newsgroups:
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lugnet.robotics, lugnet.boats
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Date:
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Sat, 28 Feb 2009 15:45:25 GMT
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Viewed:
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1670 times
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In lugnet.robotics, Claude Baumann wrote:
> ...you tried to maintain the sound pressure constant.
Since I was doing this all manually, it was by far the easiest. I realized that
a better way would be to vary the signal generator level at each frequency, but
often when trying that I simple "maxed out" the reported level from the sound
sensor at some frequency, and wanted to do that as little as possible.
> we were amazed to see that around 3kHz, the sound sometimes
> has to be louder, sometimes weaker, in order to maintain the
> constant 20 NXT-dBA. We sweeped over the range and the value
> droped and grew at neighbour frequencies.
That sounds like resonance. Perhaps in the sensor response, but at 3 kHz the
wavelength is down around 10 cm, meaning a half-wavelength at 5 cm is getting
very close to the physical dimensions of the sensor. Did you check for physical
resonance effects, perhaps within the casework?
> This leaves us puzzled. It would be a great thing, if someone
> verified this.
I'd love to, but don't have the signal generator right now. I'm very tempted to
get something like this:
http://www.pasco.com/featured-products/xplorer-glx/index.cfm
As it would satisfy nearly all of my datalogging needs when they go beyond the
NXT (higher resolution).
--
Brian Davis
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Message has 1 Reply:
 | | Re: NXT sound sensor characteristics
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| (...) Excellent suggestion!!! We'll open one sensor and try once again. (...) (URL) else interested in repeating the experiment? Philo? Claude P.S. I added a graph to the page, where the sound pressure is maintained constant. (16 years ago, 28-Feb-09, to lugnet.robotics, lugnet.boats)
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Message is in Reply To:
| | Re: NXT sound sensor characteristics
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| Thanks Brian (...) Your excellent graph shows that you tried to maintain the sound pressure constant. We did the inverse in the last graphs, where we tried to draw the curve for a constant NXT sensor value. We also repeated the experiment, and this (...) (16 years ago, 28-Feb-09, to lugnet.robotics, lugnet.boats)
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