Distance makes sound quieter and duller as air absorbs high frequencies

Evidence

Equation 1.30 shows that the sound intensity for a sound wave that spreads out in all directions from a source reduces as the square of the distance. Furthermore, this reduction in intensity is purely a function of geometry and is not due to any physical absorption process. In practice, there are sources of absorption in air, for example impurities and water molecules or smog and humidity. These sources of absorption have greater effect at high frequencies and, as a result, sound not only gets quieter but also gets duller as one moves away from a source. The amount of excess attenuation is dependent on the level of impurities and humidity and is therefore variable. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 303

Categorization

Category: Causal Relationships

• XREF: The ‘quieter and duller with distance’ insight connects to reading on soundscape tuning and keynote sounds losing their brightness with distance.

Related

• Air absorption of high frequencies makes distant voices sound duller (similarity 0.89)
• Distance from a source changes the balance between direct and reverberant sound (similarity 0.88)
• Perceived loudness falls off with distance more slowly than physical intensity does (similarity 0.87)
• Direct sound intensity falls with the square of distance from the source (similarity 0.87)
• High-frequency loss with distance provides a perceptual cue for judging sound source distance (similarity 0.85)
• Reflected sound intensity is reduced in proportion to the absorption coefficient (similarity 0.83)
• Sound pressure amplitude falls off as the inverse of distance from a source (similarity 0.82)
• Intermediate separations cause loudness to follow intensity addition instead of pressure addition. (similarity 0.81)
• Spreading sound waves weaken because their fixed energy dilutes over an expanding sphere (similarity 0.81)
• Any change in surface reflectivity, not just bumps, causes sound diffusion (similarity 0.81)
• Beyond the reverberation distance, loudness stays constant while reverberance increases. (similarity 0.81)
• Perceived loudness depends on frequency content and duration, not just sound pressure level (similarity 0.81)
• Relative loudness change provides the key auditory cue for source distance (similarity 0.81)
• Humid air carries sound faster than dry air because water molecules are lighter (similarity 0.81)
• Having access to a quiet site reduces noise annoyance without lowering physical sound. (similarity 0.81)