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teensy-audio


			
				
					
						
						
							
							
<h3>Summary</h3>
	<p>Originally, flanging was produced by playing the same signal on two synchronized
	reel-to-reel tape recorders and making one of the reels slow down and speed up by
	pressing on the flange of the reel (hence the name). This is a type of
	comb filtering, and produces a harmonically-related series of peaks and notches
	in the audio spectrum.</p>
	<p>This flanger uses a delay line, combining the original voice with only one sample from the delay
	line, but the position of that sample varies sinusoidally.</p>
	<p>The effect can be represented as:<br>
	result = sample(0) + sample(dt + depth*sin(2*PI*Fe))</p>
	<p>The value of the sine function is always a number from -1 to +1 and
	so the result of depth*(sin(Fe)) is always a number from -depth to +depth.
	Thus, the delayed sample will be selected from the range (dt-depth) to
	(dt+depth). This selection will vary at whatever rate is specified as the
	frequency of the effect, Fe. Typically a low frequency (a few Hertz) is used.
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class="top"><th>Port</th><th>Purpose</th></tr>
		<tr class="odd"><td align="center">In 0</td><td>Signal Input</td></tr>
		<tr class="odd"><td align="center">Out 0</td><td>Flanged Output</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>begin</span>(delayBuffer, length, offset, depth, delayRate);</p>
	<p class=desc>Create a flanger by specifying the address of the delayline, the
	total number of samples in the delay line (often done as an integer multiple of
	AUDIO_BLOCK_SAMPLES), the offset (how far back the flanged sample is from the original voice),
	the modulation depth (larger values give a greater variation) and the modulation
	frequency, in Hertz.
	</p>
	<p class=func><span class=keyword>modify</span>(offset, depth, delayRate);</p>
	<p class=desc>Alters the parameters in a running flanger (previously started with begin).
	</p>

	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Effects &gt; Flange
	</p>
	<h3>Notes</h3>
	<p>The longer the length of the delay buffer, the more memory blocks are used.</p>
	<p>Try these settings:<br>
#define FLANGE_DELAY_LENGTH (2*AUDIO_BLOCK_SAMPLES)<br>
and<br>
int s_idx = 2*FLANGE_DELAY_LENGTH/4;<br>
int s_depth = FLANGE_DELAY_LENGTH/4;<br>
double s_freq = 3;</p>
<p>The flange effect can also produce a chorus-like effect if a longer
delay line is used with a slower modulation rate, for example try:<br>
#define FLANGE_DELAY_LENGTH (12*AUDIO_BLOCK_SAMPLES)<br>
and<br>
int s_idx = 3*FLANGE_DELAY_LENGTH/4;<br>
int s_depth = FLANGE_DELAY_LENGTH/8;<br>
double s_freq = .0625;</p>