The example for outputing audio through only one channle doesn't work for me.. (audioDeviceWriter & audioOscillator)

I can't get this example to work at all - it's supposed to play a sine wave in one channle, and a static through the other, but I still get sound from both channles.

I've tried substituting zeros for randn to totally mute the other channel, but it had no effect either.

dev_writer = audioDeviceWriter;
sineGenerator = audioOscillator;
sineGenerator.Frequency = note2Freq(79);
count = 0;
sine = sineGenerator();
static = zeros(length(sine),1);
while count < 1000
    dev_writer([sine,static]);
    count = count + 1;
end

[jibrahim]

not sure about your set-up, but this seems to work (silence in one ear, sine in the other). If you want to hear the actual sine wave progressing, you will need to move the call to inside the for loop though:

dev_writer = audioDeviceWriter;
sineGenerator = audioOscillator;
sineGenerator.Frequency = note2Freq(79);
count = 0;
static = zeros(length(sine),1);
while count < 1000
    sine = sineGenerator();
    dev_writer([sine,static]);
    count = count + 1;
end

[Jonathan Sahar]

Thanks!

What do you mean by hearing the sine wave progressing? I thought that the generator just returns the same sine wave each time you call it to get a sine from it..

[jibrahim]

Hi Jonathan,

audioOscillator does not return the same sine wave each time you call it. When you call it, it will give you a frame of the sine wave (controlled by value of SamplesPerFrame). When you call it again, you get the next sine wave frame in time. If you stitch/plot consecutive outputs of the oscillator, you get the repeating sine wave. One output of the oscillator might just be a small part of the sine wave period, or could include multiple periods: that all depends on SamplesPerFrame and SampleRate.

[Jonathan Sahar]

Thanks for your answer. Since the sine wave is periodic (i.e. repetitive) doesn't it mean that calling audioOscillator with the same SamplesPerFrame and SampleRate will return the same waveform/frame?

At any rate - I've tested the code again, and can verify that it doesn't work as intended in terms of being one-sided: the channel that's supposed to be the only one working is much louder, but there's definitely sound coming from the other channel as well (same generated sound, not noise).

Could you advise? Thanks!

[Walter Roberson]

If the samples per frame is not an integer multiple of samples per cycle then the calls to the generator will not return the same result.

For example if you ask for 10000 samples per frame and a sample frequency of 22100 Hz then one frame would be 2.21 cycles, and the second call to the generator would start 0.21 cycles in, not at the beginning of a cycle