Widening a sound’s bandwidth makes it seem louder at equal total power

Evidence

Our impression of loudness has another surprising feature: if the sound energy in a sine tone or noise in a narrow band of frequencies is spread instead over a wide band of frequencies, it seems much louder, even though it has the same power. For example, a 60 dB band of noise 210 Hz wide centered at 1400 Hz sounds about as loud as 50 dB white noise. Again the concept of a critical bandwidth comes in, here called the critical bandwidth for loudness. Even a sine tone activates a region of the cochlea, rather than a single spot, as one might have expected from a simple resonator theory. Nearby sine waves, within the bandwidth activated by a single one, are just adding to the same band on the cochlea. But using a frequency outside the band activates a new area of the cochlea, making the sound seem louder. — Eric J. Heller, Why You Hear What You Hear- An…, 2008

Categorization

• DEFINE: Defines critical bandwidth for loudness and explains the cochlear activation mechanism behind it.
• XREF: Connects to the reader’s broader auditory-perception framework and to the psychoacoustics material on masking in chapter psychology. — connects to: Loudness rises once noise bandwidth exceeds the critical band at constant SPL.; Loudness stays constant below critical bandwidth then grows beyond it — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1034; Loudness grows with bandwidth via area tradeoff except at extreme levels — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1288 (+6 more)
• corroborated: 2 independent passages support this claim — Eric J. Heller, Why You Hear What You Hear- An…, 2008

Broader Connections

• Wider bandwidth increases perceived loudness at equal sound pressure #corroborates (0.95) — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 868
• Wideband sounds are louder than narrowband sounds at equal dB SPL #corroborates (0.93)
• Loudness grows when sound energy spills beyond a single critical band #expands (0.88) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 667
• Adding damping to a resonance paradoxically makes it more audible by widening its bandwidth #expands (0.80)
• Rapid changes in a sound’s amplitude envelope force broader spectral bandwidth #expands (0.75) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 489