# Can the pitch of a car horn be changed or manipulated? **URL:** \ **Category:** Factual Questions\ **Created:** [September 26, 2004, 2:28am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113 "2004-09-26T02:28:57Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![PaulFitzroy](https://avatars.discourse-cdn.com/v4/letter/p/2acd7d/32.png) [@PaulFitzroy](https://boards.straightdope.com/u/PaulFitzroy)\ **Post date:** [September 26, 2004, 2:28am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/1 "2004-09-26T02:28:57Z")
The other night I was sitting in my truck with a friend, waiting outside someone’s house, and I honked my horn to let him know we were there to pick him up. Then, just for the hell of it, I turned to my friend and said, “I can adjust the pitch of the horn with this little knob down here.” He got extremely excited, then I said, “just kidding.” (Man, you should have seen how disappointed he was.) Later we were seriously discussing this concept. How cool would it be to be able to play little tunes on your car’s horn? Is there any kind of device you can buy or have installed that allows you to control the pitch? My preferred device would be a knob on a slide that you can pull out or push in, like a trombone, to change the pitch. ---
**Author:** ![Dog80](https://avatars.discourse-cdn.com/v4/letter/d/6bbea6/32.png) [@Dog80](https://boards.straightdope.com/u/Dog80)\ **Post date:** [September 26, 2004, 2:53am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/2 "2004-09-26T02:53:02Z")
Most stock horns have a small screw for changing the pitch. This is from my car [http://hmaservice.com/webtech/iindex.asp?id=394877067#\_394877067](http://hmaservice.com/webtech/iindex.asp?id=394877067#_394877067) ---
**Author:** ![Finagle](https://avatars.discourse-cdn.com/v4/letter/f/b19c9b/32.png) [@Finagle](https://boards.straightdope.com/u/Finagle)\ **Post date:** [September 26, 2004, 2:54am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/3 "2004-09-26T02:54:37Z")
Or you could drive really fast and let the Doppler effect do it. ---
**Author:** ![Call\_me\_Frank](https://avatars.discourse-cdn.com/v4/letter/c/90ced4/32.png) [@Call\_me\_Frank](https://boards.straightdope.com/u/Call_me_Frank)\ **Post date:** [September 26, 2004, 3:14am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/4 "2004-09-26T03:14:14Z")
> [@Finagle](#): > > Or you could drive really fast and let the Doppler effect do it. Or drive backwards. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [September 26, 2004, 3:24am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/5 "2004-09-26T03:24:21Z")
> [@Dog80](#): > > Most stock horns have a small screw for changing the pitch. Not quite. The screw is not a pitch adjustment. Rather, it’s for adjusting the horn’s operation to optimum, which is what your link is referring to by “tone.” If you adjust the screw very far either way from optimum, it gets tinny, then goes silent. Most cars have two horns, which are of different pitches. Typically their notes are one or two semitones apart, which makes a more commanding sound than two of the same note would. If you’re replacing a car horn, find out whether it’s the high or low note; if replacing both, get one of each. Otherwise, you might end up with two same-note horns, giving a less satisfactory sound. There are electric horns available that are programmed with many different sounds. Usually these are a line or two of some song. I believe some models offer dozens of tunes, selectable by a control pad mounted inside. This is probably as close as you’ll get to “controlling the pitch.” ---
**Author:** ![t-keela](https://avatars.discourse-cdn.com/v4/letter/t/a3d4f5/32.png) [@t-keela](https://boards.straightdope.com/u/t-keela)\ **Post date:** [September 26, 2004, 3:36am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/6 "2004-09-26T03:36:56Z")
**Gary** just a thought…could you install a switch under the dash and rewire the horn where it would cut the juice going to the separate horns and toggle them so that you’d have alternating pitches. Did that make any sense? BTW-My dad had an old aa-oo-ga horn on his truck once upon a time that was pretty cool. ---
**Author:** ![W.Fikere\_Tomba](https://avatars.discourse-cdn.com/v4/letter/w/f9ae1b/32.png) [@W.Fikere\_Tomba](https://boards.straightdope.com/u/W.Fikere_Tomba)\ **Post date:** [September 26, 2004, 3:55am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/7 "2004-09-26T03:55:33Z")
I think it would be pretty rad to just have a trombonist riding in the passenger seat. ---
**Author:** ![mouthbreather](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@mouthbreather](https://boards.straightdope.com/u/mouthbreather)\ **Post date:** [September 26, 2004, 3:59am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/8 "2004-09-26T03:59:13Z")
Let your battery die. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [September 26, 2004, 4:07am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/9 "2004-09-26T04:07:11Z")
> [@t-keela](#): > > **Gary** just a thought…could you install a switch under the dash and rewire the horn where it would cut the juice going to the separate horns and toggle them so that you’d have alternating pitches. Did that make any sense? Yes, that could be done. Might be an interesting effect, reminiscent of European police sirens. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [September 26, 2004, 4:08am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/10 "2004-09-26T04:08:33Z")
[Here](http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3749568835&category=16214#ebayphotohosting) ---
**Author:** ![Dog80](https://avatars.discourse-cdn.com/v4/letter/d/6bbea6/32.png) [@Dog80](https://boards.straightdope.com/u/Dog80)\ **Post date:** [September 26, 2004, 4:30am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/11 "2004-09-26T04:30:42Z")
> [@Gary T](#): > > Not quite. The screw is not a pitch adjustment. Rather, it’s for adjusting the horn’s operation to optimum, which is what your link is referring to by “tone.” If you adjust the screw very far either way from optimum, it gets tinny, then goes silent. Thanks for the explanation. But why is that screw there in the first place? Do car horns need “re-tuning” after some time? > [@GaryT](#): > > Yes, that could be done. Might be an interesting effect, reminiscent of European police sirens. You mean the “duck” horn? ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [September 26, 2004, 6:40am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/12 "2004-09-26T06:40:12Z")
> [@Dog80](#): > > Thanks for the explanation. But why is that screw there in the first place? Do car horns need “re-tuning” after some time? I assume it has to do with the limitations of manufacturing that type of horn. The screw is essentially a movable post, which affects the vibration of a reed (or something similar). Perhaps because of subtle variations in the horns’ innards, they can’t all have optimum tone with the exact same length post in that place, and the screw allows precise adjustment to compensate for minor manufacturing differences. In my experience, often a quarter to half turn of the screw makes a quite noticeable difference in the horn tonal quality. When the horns get old, sometimes they get tinny, and adjusting the screw will improve their sound – for a while. Usually the horn fails beyond redemption not long after this. > [@Dog80](#): > > You mean the “duck” horn? I’m afraid I’m not familiar with that term. I was thinking of the emergency vehicle sounds I hear in movies set in Europe, a rapidly alternating HIGH-low-HIGH-low, as opposed to the typical emergency vehicle sirens heard in the States. ---
**Author:** ![danceswithcats](https://avatars.discourse-cdn.com/v4/letter/d/9e8a1a/32.png) [@danceswithcats](https://boards.straightdope.com/u/danceswithcats)\ **Post date:** [September 26, 2004, 7:08am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/13 "2004-09-26T07:08:26Z")
Electronic sirens in the States have that option, too-Federal calls it Hi-Lo. A duck horn doesn’t echo. Nobody knows why. 😉 ---
**Author:** ![DougC](https://avatars.discourse-cdn.com/v4/letter/d/7feea3/32.png) [@DougC](https://boards.straightdope.com/u/DougC)\ **Post date:** [September 26, 2004, 11:10am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/14 "2004-09-26T11:10:40Z")
- - - I heard once that all US car horns had to be in the same note–B flat or something. And no, this is not a joke post. …A girlfriend’s dad rebuilt a cart some years back and upon taking it for licensing, was told there was a couple problems he had to fix before they’d approve it–there was two other things they insisted on, and the inspector said that the horn was the wrong note as well and should really be tuned back in. They were military and I don’t know what _US state_ this was in, but it was in the US…? ~ ---
**Author:** ![Dog80](https://avatars.discourse-cdn.com/v4/letter/d/6bbea6/32.png) [@Dog80](https://boards.straightdope.com/u/Dog80)\ **Post date:** [September 26, 2004, 11:34am UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/15 "2004-09-26T11:34:27Z")
I guess only police cars in Greece have the “duck” horns. It is basically a horn that makes a sound very similar to those whistles used for duck hunting. It is a very strange sound, which is very different from every other car horn. They use it instead of the high-low siren when they want other cars to move out of their way, but it is not an emergency. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [September 26, 2004, 2:05pm UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/16 "2004-09-26T14:05:24Z")
> [@DougC](#): > > - > - > - I heard once that all US car horns had to be in the same note–B flat or something. And no, this is not a joke post. …A girlfriend’s dad rebuilt a cart some years back and upon taking it for licensing, was told there was a couple problems he had to fix before they’d approve it–there was two other things they insisted on, and the inspector said that the horn was the wrong note as well and should really be tuned back in. They were military and I don’t know what _US state_ this was in, but it was in the US…? > ~ I’ve been in auto repair for 30 years and haven’t heard of this. I suspect someone got mixed up about something here – the idea of an inspector determining the actual pitch of the horn doesn’t ring true. What’s he supposed to do – carry a piano with him? :dubious: ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [September 26, 2004, 2:53pm UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/17 "2004-09-26T14:53:35Z")
It’s highly unlikely that there’s any legislation governing it, but E-flat sticks in my mind for some reason, and I found this: > [@](#): > > Up until the mid 1960’s most American car horns were tuned to the musical notes of E flat or C. Since then, many manufacturers have moved up on the scale to notes F sharp and A sharp. From [http://www.cogapa.com/history.htm](http://www.cogapa.com/history.htm) That doesn’t say whether that’s the pitch of the low or high note - I would imagine it’s the low note. Maybe somebody with some pitch sense or a musical instrument and a willingness to go outside and perform a duet with their car horn could comment. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [September 26, 2004, 3:07pm UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/18 "2004-09-26T15:07:21Z")
Also, it sound like the OP might be interested in the “car horn organ” music of Wendy Mae Chambers: [http://www.wendymae.com/carhornorgan.html](http://www.wendymae.com/carhornorgan.html) (The “hear the car horn organ” link is one of the strangest renditions of “New York, New York” you are ever likely to hear) This is evidence that there’s enough variability in car horn pitches that she was able to find enough different ones to construct her instrument. ---
**Author:** ![danceswithcats](https://avatars.discourse-cdn.com/v4/letter/d/9e8a1a/32.png) [@danceswithcats](https://boards.straightdope.com/u/danceswithcats)\ **Post date:** [September 26, 2004, 4:55pm UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/19 "2004-09-26T16:55:28Z")
> [@Gary T](#): > > I’ve been in auto repair for 30 years and haven’t heard of this. I suspect someone got mixed up about something here – the idea of an inspector determining the actual pitch of the horn doesn’t ring true. What’s he supposed to do – carry a piano with him? :dubious: I’ll second that. When I had an inspection license, the State Trooper never once asked to see my pitch pipe. ---
**Author:** ![W.Fikere\_Tomba](https://avatars.discourse-cdn.com/v4/letter/w/f9ae1b/32.png) [@W.Fikere\_Tomba](https://boards.straightdope.com/u/W.Fikere_Tomba)\ **Post date:** [September 26, 2004, 5:07pm UTC](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113/20 "2004-09-26T17:07:45Z")
According to my ear-training teacher, the hi-lo siren on French ambulances is a tritone. I haven’t heard one since then, so I don’t know if he’s right. [Next page](https://boards.straightdope.com/t/can-the-pitch-of-a-car-horn-be-changed-or-manipulated/266113.md?page=2)