The first acoustic source is a speaker.
The one or more first acoustic signals consists of a single acoustic signal.
Each respective acoustic signal in the one or more first acoustic signals comprises a corresponding smooth periodic oscillation from the first acoustic source.
The one or more first acoustics signals comprises a plurality of acoustic signals including a first acoustic signal and a second acoustic signal, and the corresponding smooth periodic oscillation of the second acoustic signal has a frequency other than the frequency of the corresponding smooth periodic oscillation of the first acoustic signal.
The plurality of acoustic signals comprises five or more acoustic signals, wherein the corresponding smooth periodic oscillation of each respective acoustic signal in the plurality of acoustic signals has a unique frequency.
The plurality of acoustic signals consists of between ten and one thousand acoustic signals, wherein the corresponding smooth periodic oscillation of each respective acoustic signal in the plurality of acoustic signals has a unique frequency.
Each corresponding smooth periodic oscillation independently has a frequency between 250 Hz and 1500 Hz.
Each corresponding smooth periodic oscillation has a frequency between 250 Hz and 1000 Hz.
Each corresponding smooth periodic oscillation has a frequency between 500 Hz and 1500 Hz.
Each corresponding smooth periodic oscillation has a frequency between 500 Hz and 1000 Hz.
Emit one or more second acoustic signals from a second acoustic source concurrently to the emitting the one or more first acoustic signals from the first acoustic source.