Total surface area determines a material’s acoustic dominance more than its absorption coefficient alone

Evidence

What is the 60 dB reverberation time (T60) of a living room as a function of frequency whose surface area is 75 m2 and whose volume is 42 m3? The floor is carpet on concrete, the ceiling is plaster on lath, and both have an area of 16.8 m2. There are 6 m2 of windows and the rest of the surfaces are painted plaster on brick; ignore the effect of the door. Using the data in Table 6.1, set up a spreadsheet or table, as shown in Table 6.2, and calculate the equivalent open window area for each surface as a function of frequency. Having done that add up the individual surface contributions for each frequency band and apply Equation 6.20 to the result in order to calculate the reverberation time. — David Howard, Jamie Angus, coustics and Psychoacoustics, 1929 (#corroborates, via linked claim)

Clearly the length of time that it takes for sound to die is a function not only of the absorption of the surfaces in a room but also of the length of time between interactions with the surfaces of the room. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1824 (#expands, via linked claim)

Categorization

• XREF: connects to: Total surface area can outweigh absorption efficiency in controlling room reverberation — David Howard, Jamie Angus, coustics and Psychoacoustics, 1929; Reverberation time depends on both surface absorption and time between reflections — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1824; Surface absorption weakens early reflections below inverse-square-law predictions

Broader Connections

• Total surface area can outweigh absorption efficiency in controlling room reverberation #corroborates (0.95) — David Howard, Jamie Angus, coustics and Psychoacoustics, 1929
• Surface absorption weakens early reflections below inverse-square-law predictions #complicates (0.75)
• Reverberation time depends on both surface absorption and time between reflections #expands (0.72) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1824