Re: HUM_FORUM: Why low-frequency noise is more noticeable indoors than outdoors.
- Steve et. al.You may find these useful to understand how ground born vibration (sound waves) interact with buildings and structures. There are many other references that discuss how ILF/LF surface waves along the earth can travel long distances unsensed theen interact with a structure to casue a hum/ rumble.PS the FTA doc from the Federal Transit Adminsitration in the US. The other is from a great collection of relevant articles in Nosie and Health publications.From: technicanalyst <mr.steven.brown@...>
Sent: Friday, March 8, 2013 5:17 PM
Subject: HUM_FORUM: Why low-frequency noise is more noticeable indoors than outdoors.
Basically, a building acts as an acoustic low-pass filter, allowing low-frequency noise inside while attenuating mid-frequency noise and blocking high-frequency noise. A building can also resonate to the noise, similar to a bass drum. Because the indoors environment is quiet except for the low-frequency noise, it is more noticeable than it is outdoors, where there is no resonance and sounds of many different frequencies combine to mask the low-frequency noise. A wood-frame building is practically transparent to low-frequency noise, because wood can actually flex with the sound waves, whereas the walls of a concrete building act more as a barrier to low-frequency noise. However, even a concrete building cannot stop vibrations coming up from the ground.