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Three phyphoxphones and superposition
(10-05-2021, 10:17 PM)Jens Noritzsch Wrote:
(10-05-2021, 12:03 AM)Erik Josefsson Wrote: Further to solid's response in this thread, has anyone seen device-specific calibration data for the Audio Amplitude experiment? My Galaxy III has a "Reference SPL" default setting 60 dB (not sure what the "offset" below does?), but maybe that's a default value set for all phones?

The calibration tab could be used for a rather vague calibration of the audio amplitude, either by a reference sound of known SPL or by remembering a previously measured offset. Sebastian has tried to explain the limitations in the FAQ tab.

This gets particularly difficult now that we know about hardware variations in a device's lifetime, see (Samsung Galaxy III could be any of the four –err, at least six different– GT-I930… or a SGH-I747M, tbc?).

Thank you Jens, this brings me back to my "old phones" question since I just broke all the screens on all my Galaxy III phones. I see 52 Galaxy S5 (SM-G900F) in the sensor db and that DivestOS works on that model:

Would you buy five of those for student's experimenting? Or would you prefer any other model?

Best regards.


(10-05-2021, 08:06 PM)solid Wrote: Hi Erik,

I realized some measurements of the classical interference of (sound) waves from two "point" sources (headphones) from a smartphone using "Tone generator" of phyphox. In order to have a stronger sound I have added a small HiFi headphone amplifier as you can see on the given photo.  The result of the interference measurements by a second smartphone with "Audio amplitude" of phyphox is not so bad. It could be better but somebody from a nearby laboratory was not too much happy hearing (reasonably) amplified 4000 Hz. For comparison I have calculated the expected interference pattern for exactly the same parameters:
  • Speed of sound Cair = 344 m/s
  • Frequency f = 4000 Hz
  • Wavelength (from previous two) = 8.6 cm
  • Distance between sources L = 54 cm
  • Distance from the sources to the measurement line d = 69.5 cm
  • Interval of measurements (second phone scan) x from -50 cm to + 50 cm
Knowing the time interval of measurements (with constant speed of the phone) one can recalculate time to x.
Additionally a small modification of the "Audio amplitude" was done to see the sound intensity in the direct scale (also attached here). Unfortunately, I had to keep only French and German translations because somewhere in many others an error existed and I could not find it.


That's really beautiful!

Hey, wouldn't it be possible to compare "distance between minima" in time from the "Audio Amplitude" graph with actual location in space of the phyphoxphone if you'd have a magnet ruler? (I'm trying to figure out other uses of the magnet rulers I made for determining g since resolution at dropping speed wasn't good enough)

Best regards.


Messages In This Thread
RE: Three phyphoxphones and superposition - by Erik Josefsson - 10-08-2021, 01:24 PM

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