# Does cooler air noticeably change sound? **URL:** \ **Category:** Factual Questions\ **Created:** [October 6, 2015, 2:40am UTC](https://boards.straightdope.com/t/does-cooler-air-noticeably-change-sound/733678 "2015-10-06T02:40:29Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![syncrolecyne](https://avatars.discourse-cdn.com/v4/letter/s/f08c70/32.png) [@syncrolecyne](https://boards.straightdope.com/u/syncrolecyne)\ **Post date:** [October 6, 2015, 2:40am UTC](https://boards.straightdope.com/t/does-cooler-air-noticeably-change-sound/733678/1 "2015-10-06T02:40:29Z")
One of the signs it is fall, for me, is that at night outdoor noises (traffic, trains, aircraft, car music, other ambient sounds) start to sounds different, perhaps more “muffled,” especially at dusk when the temperature falls more quickly. I did see some information that suggests that the speed of sound drops somewhat with temperature. But would relatively minor drops have an audible effect? I might add I live in South Texas where “cooler fall weather” means it drops from around 95F in the day to 68F at night, as opposed from 100±80F - but there is still an appreciably more abrupt drop of temperatures after sunset. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [October 6, 2015, 9:39pm UTC](https://boards.straightdope.com/t/does-cooler-air-noticeably-change-sound/733678/2 "2015-10-06T21:39:26Z")
Sound travels faster in colder air because the air is denser. ---
**Author:** ![snfaulkner](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/snfaulkner/32/433_2.png) [@snfaulkner](https://boards.straightdope.com/u/snfaulkner)\ **Post date:** [October 6, 2015, 10:03pm UTC](https://boards.straightdope.com/t/does-cooler-air-noticeably-change-sound/733678/3 "2015-10-06T22:03:41Z")
> [@Quartz](#): > > Sound travels faster in colder air because the air is denser. I always thought this too, but it seems to be incorrect [https://en.wikipedia.org/wiki/Speed\_of\_sound](https://en.wikipedia.org/wiki/Speed_of_sound) Effect of temperature on properties of air Temperature T (°C) Speed of sound c (m/s) Density of air ρ (kg/m3) Characteristic specific acoustic impedance z0 (Pa·s/m) 35 351.88 1.1455 403.2 30 349.02 1.1644 406.5 25 346.13 1.1839 409.4 20 343.21 1.2041 413.3 15 340.27 1.2250 416.9 10 337.31 1.2466 420.5 5 334.32 1.2690 424.3 0 331.30 1.2922 428.0 −5 328.25 1.3163 432.1 −10 325.18 1.3413 436.1 −15 322.07 1.3673 440.3 −20 318.94 1.3943 444.6 −25 315.77 1.4224 449.1 ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [October 6, 2015, 10:20pm UTC](https://boards.straightdope.com/t/does-cooler-air-noticeably-change-sound/733678/4 "2015-10-06T22:20:36Z")
Let’s try that again: ```auto Effect of temperature on properties of air Temperature T (°C) Speed of sound c (m/s) Density of air ρ (kg/m3) Characteristic specific acoustic impedance z0 (Pa·s/m) T c ρ z0 35 351.88 1.1455 403.2 30 349.02 1.1644 406.5 25 346.13 1.1839 409.4 20 343.21 1.2041 413.3 15 340.27 1.2250 416.9 10 337.31 1.2466 420.5 5 334.32 1.2690 424.3 0 331.30 1.2922 428.0 −5 328.25 1.3163 432.1 −10 325.18 1.3413 436.1 −15 322.07 1.3673 440.3 −20 318.94 1.3943 444.6 −25 315.77 1.4224 449.1 ``` ---
**Author:** ![snfaulkner](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/snfaulkner/32/433_2.png) [@snfaulkner](https://boards.straightdope.com/u/snfaulkner)\ **Post date:** [October 6, 2015, 10:21pm UTC](https://boards.straightdope.com/t/does-cooler-air-noticeably-change-sound/733678/5 "2015-10-06T22:21:55Z")
> [@Irishman](#): > > Let’s try that again: Thanks. I was/am too lazy to…ya know…try… ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [October 6, 2015, 10:34pm UTC](https://boards.straightdope.com/t/does-cooler-air-noticeably-change-sound/733678/6 "2015-10-06T22:34:40Z")
Colour ignorance fought! ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [October 6, 2015, 11:46pm UTC](https://boards.straightdope.com/t/does-cooler-air-noticeably-change-sound/733678/7 "2015-10-06T23:46:17Z")
I read a long time ago about the specialized research on this used by Israeli (and presumably everybody else) designers of acoustic monitoring systems across the Negev desert. ---
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [October 6, 2015, 11:56pm UTC](https://boards.straightdope.com/t/does-cooler-air-noticeably-change-sound/733678/8 "2015-10-06T23:56:37Z")
It may be just things getting quieter. Birds settle down around evening, and the wind often dies down before sunset. Also, air conditioners don’t cycle as long and people drive home and stay indoors. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [October 7, 2015, 7:52pm UTC](https://boards.straightdope.com/t/does-cooler-air-noticeably-change-sound/733678/9 "2015-10-07T19:52:47Z")
Bear with me a second… The sun generally does not heat air directly. The sun heats the ground, then the ground heats the air. Similarly at night, the ground loses heat through radiation to space, and the air near the ground cools. This means that the air nearest the ground is often at a different temperature than the air above. When the surface air is cooler, it is called a temperature inversion, and can be responsible for trapping pollution (common in Denver) but there are also sonic effects. If the air near the ground is cooler, then sound near the ground is slower, and sound waves will refract toward the ground. If the ground much is warmer, then sound waves refract upward. This causes a large difference in how sound appears to carry over the ground. Sound that refracts upward (ground warmer than air) becomes muffled or inaudible over a fairly short distance. If the ground is smooth and hard (or a smooth lake) then the downward refracted sound will be reflected back up, giving a ducting effect. If you have ever clearly heard early morning fisherman speaking softly from several hundred yards across a lake, this is why. If the ground is covered with a sound deadening material, like snow, then the downward refracted sound waves are absorbed and lost. ---
**Author:** ![Richox](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@Richox](https://boards.straightdope.com/u/Richox)\ **Post date:** [October 8, 2015, 2:28pm UTC](https://boards.straightdope.com/t/does-cooler-air-noticeably-change-sound/733678/10 "2015-10-08T14:28:57Z")
Just signed up to these boards, they seem pretty cool with lots of knowledgeable and respectful people. Not the usual shitstorm on similar forums. I used to notice an effect that transmission of sounds was far more effective over long distances when the air temperature was cool in the early evening. An anecdote : I lived 2km from the nearest train station, but on a cool winters night I could and would frequently clearly hear the automated sound “PING, doors closing” (assuming it was late enough the traffic noise had died down). Exact same conditions in summer or spring, I never once heard the sound. I asked one of my mech eng lecturers at uni and he said it was similar to a thermocline type effect, and the sound would potentially refract off the temperature differential and therefore be ale to clear obstacles etc that are in nearly all urban line-of-sites of any distance. HAM radio operators can apparently also utilise a similar effect to increase their range - but thats probably just an interesting exercise a opposed to being practical. Ties in mostly with Kevbo’s comments above as well ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [October 8, 2015, 2:49pm UTC](https://boards.straightdope.com/t/does-cooler-air-noticeably-change-sound/733678/11 "2015-10-08T14:49:13Z")
> [@snfaulkner](#): > > I always thought this too, but it seems to be incorrect it is the same with viscosity of air (and gases in general). As the the temperature increases air gets more viscous. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [October 8, 2015, 3:49pm UTC](https://boards.straightdope.com/t/does-cooler-air-noticeably-change-sound/733678/12 "2015-10-08T15:49:55Z")
Walk outside from a dry home with clear nasal passages and clear nose and throat (easiest in dry, cool aiir) and your head is an a very specific state for receiving sound waves and sending them to the brain for translation into what we know as sound. Crisp, still, cool dry air lets your head/ears have the best shot at doing the work. Any moisture in your head and any wind affects your head/ears.