如何在iOS中创建脉冲声波

Question

我找到了如何创建正弦波或方波，但我无法修改以在objective-c中创建脉冲波

此代码创建正弦波，但我需要创建脉冲波。

OSStatus RenderTone(
void *inRefCon, 
AudioUnitRenderActionFlags  *ioActionFlags, 
const AudioTimeStamp        *inTimeStamp, 
UInt32                      inBusNumber, 
UInt32                      inNumberFrames, 
AudioBufferList             *ioData)
{
// Fixed amplitude is good enough for our purposes
const double amplitude = 0.25;

// Get the tone parameters out of the view controller
ToneGeneratorViewController *viewController =
    (ToneGeneratorViewController *)inRefCon;
double theta = viewController->theta;
double theta_increment = 2.0 * M_PI * viewController->frequency / viewController->sampleRate;

// This is a mono tone generator so we only need the first buffer
const int channel = 0;
Float32 *buffer = (Float32 *)ioData->mBuffers[channel].mData;

 // Generate the samples
 for (UInt32 frame = 0; frame < inNumberFrames; frame++) 
{
    buffer[frame] = sin(theta) * amplitude;

    theta += theta_increment;
    if (theta > 2.0 * M_PI)
    {
         theta -= 2.0 * M_PI;
    } 
}

// Store the theta back in the view controller
viewController->theta = theta;

return noErr;
 }

我需要修改此代码以创建脉冲波

这正是我想要创造的 Pulse wave