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The Psychoacoustics of Spaciousness

• Have you ever wondered how our brains use sound to know that we are in a large space?
• Are you stuck in a small or medium sized room for your HiFi listening or critical mixing, one that lacks a sense of sonic ambience and elbow room?
• Would you like to understand how to “trick” your brain into thinking you are in a larger room, or outdoors even?
• If you answered yes, this week is for you.

This article is a snippet from the notebook of Art Noxon, PE Acoustical, lets you see and understand the way in which reflections affect our perceptions of room size based on the time delay and sound level relative to the direct sound.

Spaciousness by Art Noxon

Psychoacoustically speaking, spaciousness = time delayed lateral reflections (TDLR).

Spaciousness is recognized by receiving late lateral reflections. Typically 20 milliseconds after the direct signal arrives and -20dB below the direct signal. A spacious space has objects located about 16 to 20 feet to the side of the listening position.

If a speaker is 10 feet from a listener and 15 feet from a side wall, the wall reflection will be -10dB below the direct signal according to: 20*log(10/34) = -10.6

A spacious signal is not a flat wall reflection. It is a reflection off of a curved object some 17 feet to the side.

Sound level at 17 feet to the side of a speaker is 20*log(10/17) = -4.6dB quieter than the direct signal @ 10 feet. A flat wall reflection would arrive at the listener an additional 6 dB quieter because the distance is doubled: -4.6 – 6.0 = -10.6dB. But we need -20dB to create spaciousness, an additional 10dB reduction compared to a flat wall reflection.

Where do we get this extra 10dB reduction?

Find out in Part 2.