Science Questions

Does fog have a dampening effect on sounds?

Sun, 14th Jun 2009

Listen Now    Download as mp3 from the show Your Science Questions

Question

Charles, New Zealand asked:

Hi, I'd like to know whether the moisture in the fog can have a dampening effect for sounds? It always feels quieter on a foggy night than a clear night, and I wonder if it's due to ambient sounds being dampened.

Answer

Chris -   It definitely does.  Yeah, great question, Charles.  The reason for that is the fog consists of tiny particles of water, which are suspended as little blobs in the air down at ground level and sound is the compression wave that travels through air.  So, when the compression wave goes through the air, itís making air molecules vibrate and theyíre passing those vibrations from one to the next like a hand shake.  If you put water molecules into air, it means that the water blobs can soak up the droplets or soak up some of the vibrations and this will attenuate or damp down quite literally (excuse the pun) the transmission of that sound through the air.  So, fog does have a sound attenuating effect and the other reason why it might that when itís foggy, people tend to slow down too.  So, people donít go out as much.  They donít play games as much.  They donít drive as much and as a result, you might see a reduction in the overall sound.. 

Multimedia

Subscribe Free

Related Content

Comments

Make a comment

Charles asked the Naked Scientists: Hi, I'd like to know whether the moisture in the fog can have a dampening effect for sounds? It always feels quieter on a foggy night than a clear night, and I wonder if it's due to ambient sounds being dampened. Love your show - great science, British accent, and bad puns - what more could one ask for? Best, Charles What do you think? Charles, Sun, 14th Jun 2009

Yes it does the dampenig effect is particularly effective for higher frequencies and ultrasound. The mass of the particles absorbs and scatters the sound energy. Many years ago tried to patent a fog detector using a cheap pair of ultrasonic transducers and some very basic signal processing.  The idea was to design a device that would automatically turn on motorway fog warning lights in poor visibility but it did not work very well and no one was really interested in paying for it. Soul Surfer, Sun, 14th Jun 2009

One point I'd like to have made when answering this question on the show (but didn't owing to lack of time) is that this is also the reason why fog horns use low frequencies.

High pitched sounds have a high frequency, which in turns means they have a short wavelength (because velocity = f x lambda). This means that to transmit a high frequency wave lots of air has to be moved back and forth, and very quickly. Consequently the losses / damping effects are high, so the sound doesn't travel very far.

But low pitched notes, with a low frequency and a big wavelength, are moving the air less fast and less often and therefore the losses are reduced. Consequently low-pitched notes as less affected by fog and will also travel further. Hence they are more ideal for a fog horn.

This also explains (at least in part) why you can hear the bass from a passing car's stereo much more than the treble.

Chris chris, Wed, 17th Jun 2009

Great, http://darvocet.socialgo.com darvocet, rfwzm, http://carinsuranceforteenagers.socialgo.com Discount car insurance for teenagers, 1916, http://downloadlimewireprofree.socialgo.com download limewire pro free now, =-))), http://aricept.socialgo.com First aricept, :-]], http://freemusicalecards.socialgo.com free musical ecards information, 558, aricept, Thu, 25th Mar 2010

Your Site Is Great!, http://www.humblevoice.com/nocreditcheckstudentloan no credit check student loan here, %-]], http://www.humblevoice.com/studentdebtconsolidationloans student debt consolidation loans, =DDD, http://www.humblevoice.com/badcreditstudentloans bad credit student loans, 698, http://www.humblevoice.com/nocreditcheckloans no credit check loans, 8OOO, http://www.humblevoice.com/highriskpersonalloans high risk personal loans now, 086, First student debt consolidation loans, Thu, 25th Mar 2010

What is it, http://militaryloans.socialgo.com military loans, 84262, http://diovan.socialgo.com Only diovan, cquv, http://percocet.socialgo.com Cheap percocet, %DDD, http://hairtransplant.socialgo.com hair transplant, 8DD, http://arthritistreatments.socialgo.com arthritis treatments, 79097, Cheap percocet, Thu, 25th Mar 2010

It is a very good thing, simple interest loan calculator simple interest loan calculator, 4163, guaranteed online personal loans guaranteed online personal loans, 371, mortgage rates predictions mortgage rates predictions, %-]], need 5000 loan overnight free need 5000 loan overnight free, 86973, personal loan for poor credit here personal loan for poor credit here, 6254, guaranteed online personal loans, Thu, 25th Mar 2010

best for you, Only no credit check car loans Only no credit check car loans, 12864, astrive student loans here astrive student loans here, =-PPP, 1000 loan payday for you 1000 loan payday for you, 772, prepaid visa travel card discount prepaid visa travel card discount, =-(, acs student loans acs student loans, %-[, Best acs student loans, Thu, 25th Mar 2010

Best Wishes!, super cheap airplane tickets for you super cheap airplane tickets for you, :(, First airline discount student ticket First airline discount student ticket, nwrfn, dirt cheap airline tickets dirt cheap airline tickets, fqiib, student loan forgiveness price student loan forgiveness price, %-(, airline discount ticket military discount airline discount ticket military discount, 371658, First airline discount ticket military, Thu, 25th Mar 2010

Have you ever been in fog? sounds travel extremely well in fog, better than clear air by far. Bill, Sat, 17th Sep 2016

See the whole discussion | Make a comment

Not working please enable javascript
EPSRC
Powered by UKfast
STFC
Genetics Society
ipDTL