Android audio applications

Signal generator 1.0.2

  • Outputs sine, pink noise, and white noise
  • Volume and frequency sliders
    • Controls are hard to grab at the edges
    • Volume control is independent from the phone’s volume control
    • Doesn’t go below 100 Hz
  • Sine waves are distorted and badly aliased at high frequencies.  THD+N measurements:
    • 100 Hz 0.149%
    • 1 kHz: 0.08%
    • 10 kHz: 7.1%
    • 20 kHz: 20.15%
    • Spectrum for 997 Hz:
    • signal generator 997 Hz
  • Although the control says “1.00 kHz” at startup, it’s actually playing 765 Hz.  Frequencies are correct after you start moving it around, though.
  • White noise level is higher than sine wave — sine wave never reaches the peak output of the phone, even at “0 dB”
  • There doesn’t seem to be any way to enter levels other than 0 dB manually, since it doesn’t let you type a minus sign.
  • White noise sounds like it’s repeating every 1.4 seconds
  • Noise is the same in both channels

Frequency generator 200909150

  • Outputs sine, square, triangle, sawtooth
  • Playing more than one sine wave causes clipping, but you can decrease the phone’s volume control
  • Default setting is 440, 444, and 448 Hz, but when played together, the waveform changes abruptly once per second
  • Sine wave THD+N:
    • 40 Hz: 1.00%
    • 440 Hz: 0.056%
    • 10 kHz: 0.051%
    • 20 kHz: 0.222%
  • I don’t know how the square, triangle and sawtooth are generated, but it ain’t right.
    • This is what the “square wave” looks like at 10 kHz:
    • freq gen square 10 kHz
    • And this is the spectrum:
    • frequency generator 10 kHz square
    • Nooot even close

(Using ExtUSB headphone cable, Adobe Audition, Audio Precision.)

4 thoughts on “Android audio applications

  1. The 10kHz square will always look bad since the sample rate is only 44.1kHz, there are only just over two samples in a 10kHz signal. After low pass filtering in the DAC it should look like a sine as the next harmonic (the 3rd) is already fully suppressed. To get a better indication of the square wave capability run it at 1kHz.

    I do agree with you that the frequency spectrum doesn’t look right. There should be no sub-harmonics.

  2. I just uploaded my own signal generator app for android. Its called FuncGen, if you want please check it out.

  3. Pingback: Playing an arbitrary tone with Android - Android Questions - Developers Q & A

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