So how low can you hear? - AVS Forum
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post #1 of 6 Old 09-15-2013, 08:49 PM - Thread Starter
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OK this will be a little different – it involves listening to live sound. During the early hours of the morning, typically a Sunday at 4 am, I can hear the rumble of diesel locomotives at the Point Roberts Super Port here in Vancouver. Google Earth shows that they are about 7 Km from where I'm pretending to sleep. What's interesting is just how loud they sound against the silence of this residential neighborhood.

Bear in mind that these trains, typically 150 cars of coal, are just idling as they move through the offloading stages. China needs lots of coal and Canada is delivering millions of tonnes of it. Who gives a damn about Global Warming.

So all I'm hearing is just engine noise at idle– at 7 kilometers. As a point of reference, a Google search pulled up a South African document which indicate that a 3000 HP locomotive at 30 m would have 65 – 68 db A sound pressure. (you have to love the Internet!)

http://www.tshwane.gov.za/Services/EnvironmentalManagement/Noise%20Management%20Documents/NoiseAppendixA.pdf

OK, so the question. Just how low, how far, how quiet, can you actually hear?

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post #2 of 6 Old 09-15-2013, 10:05 PM
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Quote:
Originally Posted by Trendy View Post

... Just how low, how far, how quiet, can you actually hear?

How low and how quiet have already been determined on the equal loudness curve. (See bottom of page at: http://www.phys.unsw.edu.au/jw/hearing.html)

I find how far is greatly affected by wind speed and direction.
I live less than 3 km from the train bridge crossing at Pitt River, and even though the trains go over it dead slow at night time, it can range from disturbingly loud to totally silent depending on wind direction.

Try to take note of the wind direction in your neighborhood the next time it seems louder than normal.
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post #3 of 6 Old 09-16-2013, 06:36 AM
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Quote:
Originally Posted by Trendy View Post

OK this will be a little different – it involves listening to live sound. During the early hours of the morning, typically a Sunday at 4 am, I can hear the rumble of diesel locomotives at the Point Roberts Super Port here in Vancouver. Google Earth shows that they are about 7 Km from where I'm pretending to sleep. What's interesting is just how loud they sound against the silence of this residential neighborhood.

In general residential neighborhoods aren't all that quiet. One word: HVAC.

I did some research on the SPL created by diesel locomotives, and I was surprised. I found numbers like Peak 95 dB in the cab, 85 dB around the locomotive, and 78 dB max in the cab while cruising.
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Bear in mind that these trains, typically 150 cars of coal, are just idling as they move through the offloading stages. China needs lots of coal and Canada is delivering millions of tonnes of it. Who gives a damn about Global Warming.

So all I'm hearing is just engine noise at idle– at 7 kilometers. As a point of reference, a Google search pulled up a South African document which indicate that a 3000 HP locomotive at 30 m would have 65 – 68 db A sound pressure. (you have to love the Internet!)

http://www.tshwane.gov.za/Services/EnvironmentalManagement/Noise%20Management%20Documents/NoiseAppendixA.pdf
Quote:
OK, so the question. Just how low, how far, how quiet, can you actually hear?

Depends on lots of thing including atmospheric conditions. If there is a certain arrangement of layers and temperatures, things that are far away can sound like they are in your back yard.

The terrain matters, as well. My wife and I hike and camp in Agawa canyon up in Ontario and there is a train track that is up the canyon wall from the trail and camp sites. The tracks run 0.25-0.50 miles uphill from the trail and campsites and sometimes you see the train and not hear it.

The nearest train tracks to my house are 5 miles away, basically about the same. I hear the trains in the early morning when the weather conditions are right.

Other kinds of large Diesel engines can be quieter. I used to live 0.5 miles from the mutli-megawatt multi-engine municipal Diesel power plant in Homestead, FL Rarely heard it. It ran far slower.
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post #4 of 6 Old 09-16-2013, 10:17 AM
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Originally Posted by arnyk View Post

In general residential neighborhoods aren't all that quiet. One word: HVAC.....

What is considered quite in every day life is relative at the time. We NEVER experience anything near quite (lower than 30dB) in real life.To the OP if you ever get the chance experience an anechoic chamber. It will freak you out. It sounds like your heart is going to explode and is a jack hammer in your ears.
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post #5 of 6 Old 09-16-2013, 11:55 AM
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Quote:
Originally Posted by William View Post

Quote:
Originally Posted by arnyk View Post

In general residential neighborhoods aren't all that quiet. One word: HVAC.....

What is considered quiet in every day life is relative at the time. We NEVER experience anything near quiete (lower than 30dB) in real life.

Agreed. And getting away from civilization is not necessarily any help. Wind blowing through trees and waves on a beach range from just as noisy as being in the house, to nearly deafening.
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To the OP if you ever get the chance experience an anechoic chamber. It will freak you out. It sounds like your heart is going to explode and is a jack hammer in your ears.

While many anechoic chambers are also quiet rooms, and the absence of reflections is a surely different listening experience, there is no natural law that says that an anechoic chamber has to be a quiet room, or vice-versa. Example: the far end of a dry cave. Its quiet but it is probably far from anechoic.
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post #6 of 6 Old 09-16-2013, 03:26 PM
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There are a lot of variables involved in the actual range of hearing. Environment changes everything, both reduces and enhances any sounds, ground cover absorbs or bouces certain frequencies more than others and buildings, water and hills can redirect or completely block sounds. Wind speed and direction naturally can carry sounds far beyond normal ranges and low clouds and fog and snow will greatly reduce all sounds. Rain is pretty noisy in itself so that would reduce ranges too because of the increased ambient level.
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