- BS?

Years ago we had a guy in the band who claimed to have perfect pitch. He did have a fine ear for tuning so we let him tune all our guitars before each gig - easier for the rest of us (before digital tuners came out). However, when compared to a real tuner, or piano, or tuning fork he was consistently flat by about a semitone - always the same, but flat. First he claimed everybody & every device was wrong and only he was right. That wore a little thin, so then he said it had to do with elevation....he was from New York City, essentially sea level, but we were living at about 3000' in a desert climate. He wanted to blame his flatness on the difference in air pressure, an argument none of us could intelligently counter. So we fired him.

But I was just reading some stuff on early supersonic flight and it was mentioned how sound travels slower thru less dense air. This reminded me of the old argument and I wondered if anybody has some insight on this?

That's true, and so is perfect pitch. My mom has it, and it's a double edged sword. If an instrument is perfectly in tune she's got no problems, but once she was asked by my dad to play a piano at a friend's house, and it was out of tune. She was unable to play it, because what she was hearing did not match what she was playing. My dad, who didn't understand such things, was furious with her for embarrassing him after he'd bragged on her musical ability.

As for tuning guitars to a person's ear, there's a reason it doesn't work, and it's called the tempered scale. Guitars are tuned to a tempered scale, and ears are not.

If I'm jamming with mom, I don't have to call out keys or changes...as long as we're in tune, she knows what's being played almost instantly, and can jam right along on tunes she's never heard.

However, I don't tune to her ears, I tune to her keyboard.

~Rich See my gear at the link!

Doppler effect. Catch the sound of a moving train lately?

Along with perfect pitch there is perfect relative pitch where someone can identify intervals. So he got the starting note wrong, he was still able to tune by ear pretty well.

I think I have a great ear (I'll never claim perfection). It can be a curse. Anything out of tune, even slightly, is painful for me. Because of this, I have a love/hate relationship with my guitars. I am constantly tweaking. When I got a new nut put on my SG, I sat with my tech while he filed the slots. I hated the sound of the open D on that guitar. We checked the fretted notes on his professional grade tuner and one note was slightly off. It sounded WAY off to me. He commented that if that bothered me then I would never be happy with a SG...

Pitch is independent of ambient air pressure. Pitch is given by the frequency (Hz) of the sound. Someone with PP could identify a middle C (261.2 Hz)whether it was played at the top of Everest or in the Qattara Depression. It would sound the same.

The guy is a bullshitter and you were right to fire him.

Again...Look up the Doppler effect.

Yep, which raises or lowers the pitch accorting to whether the source is moving towards or away relative to the listener. If the source is moving towards the listener the sound waves lengths are compressed, raising the frequency. If moving away, the waves are stretched, reducing the frequency. For a static source-listener scenario, the audible frequency is totally dependent upon (for a stringed instrument), the frequency of vibration of the string.

Where is gets complicated is where there is a noticeable pressure gradient between the source and the listener. Think of a jet breaking the sound barrier high in the atmosphere where the air is thinner, and sound travels more slowly. As the pressure wave approches the listener on the ground, it will indeed speed up, the individual waves passing the ground-based listener with greater frequenccy. The sound of the sonic boom at ground level will be at a higher frequency than where it was generated.

The doppler effect only governs the relative frequency between two objects in different inertial frames. Translation? It's only when there is relative motion between the sender and receiver, ie, when or both one is moving forward or away from the other.

Take the infamous wave equation C=f * λ, where C (often the speed of light when refering to electromagnetic waves, but here just the speed of wave propogation), f is frequency and lambda(λ) is the wavelength. Since, the wavelength of a wave varies directly with the speed for any given frequency in the same medium, we find C & f directly proportional. Then it is necessary for lambda (the frequency) to remain the same to satisfy the equation. Source?
http://www.sasked.gov.sk.ca/docs/physics/u2b12phy.html

However, if one or both objects are moving with respect to each other we are not directly modifing the wave, which would effect the amplitude or wavelength. Then the only thing that can change is the frequecy, hence the doppler effect.

Therefore, it doesn't matter where you are. A 440 is A 440 wherever you go. However, it is only when you are in relative motion when the doppler effect takes place. I suggest *you* look up the doppler effect. They were right in that the guy was wrong about being perfect pitch.

Unless if he, when at higher altidudes was aways moving away from you at significant velocities.

Wether that warranted him being fired is another matter

There will be no change in frequency. The speed of a wave is proportional to the properties of it's propagation matter.
http://www.ndt-ed.org/EducationResources/HighSchool/ Sound/speedinmate...

Usually the speed of sound tied closely with density. That's why you can hear a far away train by holding your ear to the tracks. Experiment: get a tuning fork, tap it regularly and hold it up to your ear. Observe the pitch. Next put your ear to a solid surface, a wall will do, and tap the fork and place it against the wall several feet away. Notice the the pitch. It's the same.

But since the sound wave went through the wall, and the speed of sound through solid rigid materials is *much* faster than through air, according to your theory, the pitch would have sounded alot higher.

If you'd like me to do the calculation for you of how much higher it would have been, I'd be glad to, but needless to say it would have been quite noticable.

However, it didn't. The wavelength of the soundwave changed. Not the frequency. Try it for yourself.

Remeber: the wavelength varies proportional with speed through a material where the speed changes, and frequency will remain the same. If the material is fixed at a certain speed (like the vaccum of space), then wavelength and frequency have a inversely proportional relationship.

Sorry for all the math.

He's right. That's it.

inline
http://www.ndt-ed.org/EducationResources/HighSchool/ Sound/speedinmate...

I knew there was a flaw somewhere in my thought experiment. You are right of course, wavelength and propagation velocity change, not frequency.