= Auditory feedback
<Auditory feedback> is information obtained by <hearing> the sound produced by one's own action. During vocal control, it can be compared with an intended or learned sound, allowing later production to be adjusted. Hearing another individual's demonstration supplies an example to learn; hearing the consequences of one's own production supplies feedback. The two experiences have different causal roles.
A controlled birdsong experiment manipulated that distinction. Adult <Bengalese finches> wore custom headphones; a cage microphone fed sound-processing hardware that shifted the pitch of their own songs before playback. The birds changed their produced pitch in the compensatory direction, and pitch returned toward baseline when the perturbation was removed. Stable adult song therefore remained subject to active correction under these conditions.<Adult birdsong is actively maintained by error correction by Samuel J. Sober and Michael S. Brainard>[Abstract and Figure1: apparatus, pitch shift and recovery]{ref}
For an original numerical illustration, a playback system that multiplies frequency by $2^{1/12}$ turns a $500$-hertz component into about $529.7$ hertz. To cancel that multiplicative shift exactly, production would need to be about $500/2^{1/12}=471.9$ hertz. These values illustrate the direction of an ideal compensation, not a claim that the birds achieved complete correction.
Altered <auditory feedback> can thus probe a control mechanism without simply disabling hearing. Timing, pitch and loudness are distinct perturbations, and a response to one manipulation does not establish identical control rules for every species or vocal behavior.
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