Noise-like sounds have non-repeating waveforms and continuous, inharmonic spectra

Evidence

By way of contrast and to complete the story, sounds that have no definite musical pitch (but a pitch nevertheless—see what follows) associated with them, such as the “ss” in sea (Figure 3.9 later in the chapter), have an acoustic pressure waveform that does not repeat regularly, and is often random in its variation with time and is therefore not periodic. Such a waveform is referred to as being “aperiodic” (see Chapter 1). The spectrum of such sounds contains frequency components that are not related as integer multiples of some frequency, and there are no harmonic components. The spectrum will often contain all frequencies, in which case it is known as a “continuous” spectrum. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 822

Categorization

• DEFINE: Defines aperiodic waveforms and continuous spectra in contrast to periodic tonal sounds.
• XREF: connects to: Continuous-spectrum noises can carry pitch perceived from spectral peaks — David Howard, Jamie Angus, coustics and Psychoacoustics, 900; Periodic sounds give line spectra while aperiodic sounds give continuous spectra — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 822; Aperiodic sounds emerge when continuous in-between frequencies cancel periodic repeats — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 459 (+2 more)

Broader Connections

• Periodic sounds give line spectra while aperiodic sounds give continuous spectra #corroborates (0.95) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 822
• In-filling components between harmonics cancel wave repetition to represent aperiodic sounds #expands (0.80) — David Howard, Jamie Angus, coustics and Psychoacoustics, 455
• Periodicity in the acoustic waveform determines whether a sound is perceived as pitched. #corroborates (0.80) — David Howard, Jamie Angus, coustics and Psychoacoustics, 828
• Aperiodic sounds emerge when continuous in-between frequencies cancel periodic repeats #qualifies (0.75) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 459