Doppler effect on recordings/in concert halls

[A Lark Ascending]

Something that has always disturbed me.

On some recordings where you get a loud chord followed by silence (or quiet music) I hear an echo but at a slightly lower pitch. Creates an impression of 'out of tune'. I thought this was a recording issue but noticed it in the Royal Albert Hall last month a couple of times.

Seems to happen on some recordings more than others, I assume due to the resonance of the recording venue. And becomes especially apparent when listening with headphones.

This recent release really has me wincing (not the music or performance, just that effect):

Is it just my battered ears?

(Apologies to anyone who has never noticed this and now starts hearing it!)

Edited September 7, 2014 by A Lark Ascending

[Daniel A]

I hear it in some churches. Where I've noticed it, it seems as if the echo from the organ is at a slightly higher pitch.

[lipi]

I am not sure what you are hearing exactly, but just a few quick notes.

The Doppler effect does not play a role here. Source and receiver (the microphone here) are not moving relative to each other, so there is no Doppler shift.

I am off-hand unaware of another physical effect able to change the pitch proper of a pure tone. However, what *is* possible is to strengthen or attenuate partial harmonics of a non-pure tone (and all tones you hear in music are non-pure--they're all combinations of partial harmonics, of a base tone and its "overtones"). In particular, lower harmonics tend to survive a lot better when bounced between walls or filtered between pillars and people and things. You shouldn't be changing the pitch of the tone when you lose harmonics like that, but you will certainly change its timbre. The echoes will be relatively rich in low partials, and poor in high ones.

Another possibly relevant effect is flutter echo: sounds bouncing between two flat surfaces facing each other. If you clap in an empty church, you'll hear a few more claps--that's the flutter echo. The frequency of these is usually low (the echo repeats a few times per second), but I don't remember my Helmholtz et al. well enough to know whether that can have funny physiological effects. (In other words: I know the physics part, but I don't remember what happens once it makes it to your auditory cortex: can such an echo result in bizarre pitch bending perception? I don't know.)

If you really want to figure it out, Rayleigh ("The Theory of Sound"), Helmholtz ("On the Sensation of Tone"--essential, but old-fashioned and hard to slog through), Sabine (various papers), and Benade ("Fundamentals of Musical Acoustics"--probably the best place to start) are your men. If you haven't really read much about the physics of sound and music before, start with Tyndall ("The Science of Sound") or Jeans ("Science and Music"), maybe, They'll start you off slowly (Tyndall especially).

[A Lark Ascending]

Many thanks both!

I'm afraid I last did physics in 1969 so anything technical is going to lose me. Think I get the gist of your suggestions, Alex.

Just curious if others are disturbed by this. I'd describe the effect as causing 'discomfort' - a bit like 'wow' on record players but the pitch just drops rather than oscillating.

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Interesting how we can adjust expectations. Listening to recordings from early 20thC to the 50s you expect pitch insecurity and so just listen through it (Ellington sounds amazing, regardless of limitations of the recording techniques of the time). But in a modern recording where you expect absolute fidelity....

Edited September 7, 2014 by A Lark Ascending