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Wave lenght and room size (1 Viewer)

Marcelo T

Stunt Coordinator
Joined
Oct 21, 2001
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I had a discussion with a friend about bass frequencies and he told me that a very large room would be necessary to form a 20hz wave. He said all we hear is the harmonics from that wave. Is this true? I have a 19x10 room, so what would be the lowest frequency I’d be able to hear on my room?
 

Dustin B

Senior HTF Member
Joined
Mar 10, 2001
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3,126
Absolutely postively untrue. Huge myth that couldn't be any farther from the truth. Here is my response from another thread on this topic.

Sound is just varing air pressure over time. As the wave passes by you, the pressure changes and you hear it. The driver will start the wave propagating, once it passes your ear you will percieve it. Not having enough space for the entire wave to exist in a straight line doesn't matter.


These pressure waves will also bounce off walls, no matter what their frequency. So in some cases many full wavelengths will pass by your ear before you start to hear the first reflextions off a boundary. But with waves longer than room dimensions it's very possible that the begining of the wave will pass your ears twice before the end of the wave reaches it. However, this doesn't mean you won't be able to hear it.


The speed of sound is roughly 1130 feet per second, so:

16hz - 70.6' wave length
20hz - 56.5'
30hz - 37.7'
50hz - 22.6'
70hz - 16.2'

My room is 18' long, most drum, bass guitar and explosions on CDs and DVDs would sound pretty lame if I wasn't getting anything below 60hz. And the explosions, drums and bass guitar all sound rather nice from my Tempest sonosub.

Then take headphones for instance. Say the distance from the driver to your ear is 2", which is very generous. Then headphones couldn't produce any sound below 6767hz by your contention. This essentially means they couldn't reporduce any voices (except for maybe Celine Dion :p)) and the majority of instruments' ranges.

I've listened to 20hz tones on my headphones and I've listened to 20hz test tones on my sub in my 18' long room.

The exception to this is if the wave is the perfect length so that the reflextion perfectly cancels itself on the way back (standing wave pattern formed). If you are sitting in the resulting null, then you won't be able to hear that frequency as a result of the rooms length. But only with that specific frequency and it's harmonics, with you sitting at a specific place in the room.

 

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