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This is a discussion on Does the winter weather increase exhaust drone? Increase power? within the New Member Hangout forums, part of the Community - Meet other Enthusiasts category; Originally Posted by wrx650 I think it would be the opposite. Sound travels faster in denser fluids. Sent from my ...

  1. #16
    MAINEiac 11blackSTi's Avatar
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    Quote Originally Posted by wrx650 View Post
    I think it would be the opposite. Sound travels faster in denser fluids.


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    Plus, there is not enough air between our exhaust and our ears to make a difference for any changes in air density!

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    Registered User wrx650's Avatar
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    Does the winter weather increase exhaust drone? Increase power?

    Quote Originally Posted by 11blackSTi View Post
    Plus, there is not enough air between our exhaust and our ears to make a difference for any changes in air density!
    Yeah very true. The density changes are basically negligible.


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    Registered User drkhead's Avatar
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    Quote Originally Posted by Axex View Post
    If the air is denser when cold wouldn't it be more difficult for sound waves to travel through, which would make it quieter? I'm sure the humidity plays a hand in this as well. I took an acoustics class, but I wasn't the best student and I don't think I have that book anymore
    I'm an audiologist.

    Density of air has very little effect on intensity of sound. In fact, you won't find many atmospheric conditions in the USA that will affect sound much at all for our human ears to realize.
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    Administrator RayfieldsWRX's Avatar
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    I was talking not so much about the sound, and more about vibration science. When you go down the road, vibrations from your engine and exhaust note will cause "resonance", that is, a frequency is there that makes things really vibrate hard. This can be responsible for the drone that many cars have, at a given speed. Temperature and air pressure can affect the frequency at which resonance happens, so...in theory...it's possible that in colder weather, your highway cruising speed may now be "the magic frequency".

    Sorry...engineering school pokes its head up through my psyche, once in a while. I could be completely wrong about the affect that you're seeing.

    As for denser air, no one can convince me that it doesn't have a profound effect on my turbocharger. Once temps are below 60 degrees, it's like a different car.
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    Registered User wrx650's Avatar
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    Quote Originally Posted by RayfieldsWRX View Post
    I was talking not so much about the sound, and more about vibration science. When you go down the road, vibrations from your engine and exhaust note will cause "resonance", that is, a frequency is there that makes things really vibrate hard. This can be responsible for the drone that many cars have, at a given speed. Temperature and air pressure can affect the frequency at which resonance happens, so...in theory...it's possible that in colder weather, your highway cruising speed may now be "the magic frequency".

    Sorry...engineering school pokes its head up through my psyche, once in a while. I could be completely wrong about the affect that you're seeing.

    As for denser air, no one can convince me that it doesn't have a profound effect on my turbocharger. Once temps are below 60 degrees, it's like a different car.
    I couldn't agree more on the colder air. There is a very large drop in enthalpy for air between a "warm day" and a "cold" day. I am studying mechanical engineering and love thermodynamics . What type of engineer are you?
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    Administrator RayfieldsWRX's Avatar
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    Degreed as a mechanical...worked as a machine designer for a year or so, and switched to controls/electrical...did that for 13 years, then switched to a quality management position. It's the nice thing about engineering...it opens the doors, and then you figure out where you want to go.
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    Registered User wrx650's Avatar
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    Does the winter weather increase exhaust drone? Increase power?

    Quote Originally Posted by RayfieldsWRX View Post
    Degreed as a mechanical...worked as a machine designer for a year or so, and switched to controls/electrical...did that for 13 years, then switched to a quality management position. It's the nice thing about engineering...it opens the doors, and then you figure out where you want to go.
    That's cool and I agree, a lot of options.


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    Registered User Axex's Avatar
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    Quote Originally Posted by wrx650 View Post
    I think it would be the opposite. Sound travels faster in denser fluids.
    Ah maybe, I did not realize this. Thanks.

    Quote Originally Posted by drkhead View Post
    I'm an audiologist.

    Density of air has very little effect on intensity of sound. In fact, you won't find many atmospheric conditions in the USA that will affect sound much at all for our human ears to realize.
    Oh cool, thanks for setting us straight! Yea I only took the one class on acoustics but I can't seem to recall us talking about changes in air density really.

    Quote Originally Posted by RayfieldsWRX View Post
    I was talking not so much about the sound, and more about vibration science. When you go down the road, vibrations from your engine and exhaust note will cause "resonance", that is, a frequency is there that makes things really vibrate hard. This can be responsible for the drone that many cars have, at a given speed. Temperature and air pressure can affect the frequency at which resonance happens, so...in theory...it's possible that in colder weather, your highway cruising speed may now be "the magic frequency".

    Sorry...engineering school pokes its head up through my psyche, once in a while. I could be completely wrong about the affect that you're seeing.

    As for denser air, no one can convince me that it doesn't have a profound effect on my turbocharger. Once temps are below 60 degrees, it's like a different car.
    You know that's a good point that I hadn't considered. I'm not sure how noticeable that would be, but there are guys that sit near me at work that would definitely know! Maybe I'll ask one of them this week. Yes, air temperature has a big effect on the engine performance and it's awesome.

    Quote Originally Posted by RayfieldsWRX View Post
    Degreed as a mechanical...worked as a machine designer for a year or so, and switched to controls/electrical...did that for 13 years, then switched to a quality management position. It's the nice thing about engineering...it opens the doors, and then you figure out where you want to go.
    Cool! I graduated not too long ago in Mechanical Engineering. I enjoy meeting others and hearing about what they've done with it.

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    Registered User EndlessSea's Avatar
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    you mentioned elevation. were you going uphill? you need more throttle to maintain the same speed when heading up an incline.

    more throttle=more noise
    even in 5th gear

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    Registered User CharlieBronson08's Avatar
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    Quote Originally Posted by EndlessSea View Post
    you mentioned elevation. were you going uphill? you need more throttle to maintain the same speed when heading up an incline.

    more throttle=more noise
    even in 5th gear
    Yes, definitely a lot of uphill climbing. That definitely made it worse. I was certain that even around the flat spots the drone was worse but now after some time, I'm pretty sure that the altitude may have had very little influence.

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    Registered User CharlieBronson08's Avatar
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    Quote Originally Posted by wrx650 View Post
    Sound travels faster in denser fluids.
    Quote Originally Posted by drkhead View Post
    I'm an audiologist. Density of air has very little effect on intensity of sound. In fact, you won't find many atmospheric conditions in the USA that will affect sound much at all for our human ears to realize.
    But sounds waves travel faster in warm air and slower in cold air. So, therefore, if sound goes from warm to cold air, would the sound waves not be closer together when they hit the cold air thus changing the tone? And if the sound moves more slowly in the cold air, shouldn't it be easier to hear sounds in the cold?

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    Administrator RayfieldsWRX's Avatar
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    At 30 degrees F, the speed of sound is about 330 m/s. At 70 degrees, it's 344 m/s...a difference of about 4%. Doesn't seem like it would make a significant difference in audibility to the human ear.
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    Registered User wrx650's Avatar
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    Does the winter weather increase exhaust drone? Increase power?

    Quote Originally Posted by RayfieldsWRX View Post
    At 30 degrees F, the speed of sound is about 330 m/s. At 70 degrees, it's 344 m/s...a difference of about 4%. Doesn't seem like it would make a significant difference in audibility to the human ear.
    I checked that out too and I don't think you're right about not being able to hear the difference.


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  15. #29
    Administrator RayfieldsWRX's Avatar
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    The difference in what? The frequencies should be the same, simply traveling to your ear in a time that is 4% less.

    Let's say that the distance from your ear to the exhaust system is about 3 meters. (It's probably less, but I'll err towards what you're saying) The difference from 30 degrees versus 70 degrees means that the sound would reach your ear in 8.7 msec, versus 9.1 msec. I don't see why it would make a difference in what you hear. Are you referring to some other phenomenon?

    Resonance makes much more sense, to me.
    Last edited by RayfieldsWRX; 01-26-2013 at 09:30 AM.
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    Registered User CharlieBronson08's Avatar
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    Why are you able to hear sounds more clearly in the cold? I believe that is an agreed upon phenomenon but I'm not sure of the mechanism.

    Resonance definitely is a viable factor contributing to differences in experience. I'm wondering also about the refraction of sound from warm to cold to warm. Perhaps there is not enough space from the exhaust to your ear? Also, it may be sound bouncing off the road or inside of the car, thus why one poster indicated that the exhaust is louder when people are in the vehicle.

    I'm completely ignorant of physics so just throwing possibilities that may have no relevance what so ever.

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