Loudness stays constant below critical bandwidth then grows beyond it

Evidence

A narrowband noise with a fixed centre frequency is used as the reference sound, to which the subject compares the test sound, band-limited noise whose sound pressure level and centre frequency are equal to the reference sound (see Figure 9.15). The change in perceived loudness is measured with some psychoacoustic test, and a schematic plot of such a test result is shown in Figure 9.16. Interestingly, the loudness is constant up to a certain value of bandwidth (Fastl and Zwicker, 2007). This bandwidth is 160 Hz for the center frequency 1 kHz, as shown in the figure, beyond which the loudness increases steadily. The knee point in the plot is thought to be the position where the test sound’s spectrum spreads over more than a single critical band Figure 9. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1034

A fourth method for determining the critical bandwidth is that of loudness measurement as a function of bandwidth for constant sound pressure level. … The result shows that loudness is constant as long as the bandwidth of the band-pass noise is smaller than a critical value, in this case 300 Hz at a centre frequency of 2 kHz, which corresponds to the critical bandwidth at that frequency. Beyond that bandwidth, loudness increases by up to a factor of three for very large bandwidths. At that point, the loudness of a broad-band noise is reached. The important condition for these measurements is the fact that the overall sound pressure level remains constant, i.e., the density of the sound intensity has to be reduced as the bandwidth of the noise is increased. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 910

A classic method to measure the frequency resolution of human hearing is outlined in this section. A narrowband noise with a fixed centre frequency is used as the reference sound, to which the subject compares the test sound, band-limited noise whose sound pressure level and centre frequency are equal to the reference sound (see Figure 9.15). The change in perceived loudness is measured with some psychoacoustic test, and a schematic plot of such a test result is shown in Figure 9.16. Interestingly, the loudness is constant up to a certain value of bandwidth (Fastl and Zwicker, 2007). This bandwidth is 160 Hz for the center frequency 1 kHz, as shown in the figure, beyond which the loudness increases steadily. The knee point in the plot is thought to be the position where the test sound’s spectrum spreads over more than a single critical band Figure 9. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1034

Categorization

• DEFINE: This operationally defines the critical band: the bandwidth below which loudness is constant regardless of spectral spread.
• CANDY: That loudness is flat until bandwidth crosses roughly 160 Hz at 1 kHz, then climbs, is a crisp, quotable fact about hearing.
• corroborated: 4 independent passages support this claim — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1034; Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 910
• XREF: connects to: Loudness rises once noise bandwidth exceeds the critical band at constant SPL.; 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; Loudness grows when sound energy spills beyond a single critical band — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 667 (+7 more)

Broader Connections

• Loudness grows when sound energy spills beyond a single critical band #corroborates (0.90) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 667
• Loudness grows with bandwidth via area tradeoff except at extreme levels #corroborates (0.85) — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1288
• Widening a sound’s bandwidth makes it seem louder at equal total power #corroborates (0.85) — Eric J. Heller, Why You Hear What You Hear- An…, 2008
• Wider bandwidth increases perceived loudness at equal sound pressure #corroborates (0.80) — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 868
• Loudness is the summed specific loudness across critical-band rates, not the raw spectral level #expands (0.80)
• Total loudness is the integral of specific loudness over critical-band rate #expands (0.80) — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1250
• Masking acts within critical bandwidths, leaving distant-frequency sounds unaffected #expands (0.75) — Eric J. Heller, Why You Hear What You Hear- An…, 2009