Acoustics of baroque, classical and modern flutes

modern flute
B foot


Music Acoustics UNSW

modern B modern C classical C classical D classical flared baroque B3 B3
C4 C#4 D4 D#4 E4 F4 F#4 G4 G#4 A4 A#4 B4
C5 C#5 D5 D#5 E5 F5 F#5 G5 G#5 A5 A#5 B5
C6 C#6 D6 D#6 E6 F6 F#6 G6 G#6 A6 A#6 B6
C7 C#7 D7 D#7 E7 F7 F#7 multiphonics


a key depressed
a key not depressed
a part of the mechanism that is not normally touched
Details in fingering legend.

Acoustic schematic
a closed tone hole
an open tone hole

Non-specialist introduction to acoustic impedance
Non-specialist introduction to flute acoustics

Impedance spectrum of a modern flute with a B foot measured at the embouchure hole using fingering for C4. Z is plotted in dB, i.e. 20 log(Z/Pa.s.m-3). The impedance phase spectrum of C4 has also been measured.

The second lowest note, so one tone hole open. Comparing this with C4 on the C foot flute, one can see that even one open tone hole has a noticeable filtering effect above about 2 kHz. The impedance curve is still rather regular and harmonic, and the first 7 or 8 minima can be played (C4, C5, G5, C6, E6, G6, A/6, C7), but usually flute players only play the first, for which the higher minima aid the production of harmonics.

In the sound spectra below (forte, mezzopiano and pianissimo), notice that the higher dynamic levels are achieved mainly by increasing the power in the higher harmonics, with little change in the power of the fundamental. Human ears are more sensitive to the higher harmonics, so this technique is effective for making the instrument louder. Stronger high harmonics mean a more non-linear vibration of the jet, while the pianissimo spectrum is closest to a sine wave and corresponds to a more linear jet-bore interaction.

Sound forte

Sound spectrum of a modern flute with a B foot played using fingering for C4 forte.

Sound Clip forte

You can hear C4 forte played by Geoffrey Collins.

Sound mezzopiano

Sound spectrum of a modern flute with a B foot played using fingering for C4 mezzopiano.

Sound Clip mezzopiano

You can hear C4 mezzopiano played by Geoffrey Collins.

Sound pianissimo

Sound spectrum of a modern flute with a B foot played using fingering for C4 pianissimo.

The first few maxima in this sound file show the sharp, narrow peaks of the spectrum of the vibration of the air-jet as it interacts with the flute. The maxima at high frequencies, however, are much weaker. Note however that they are also less narrow. For this note, the air jet is oscillating in a more nearly sinusoidal way, and so has much less power in the high harmonics. On the other hand, the turbulent motion of the air jet can still excite waves at frequencies where the impedance is low.

Sound Clip pianissimo

You can hear C4 pianissimo played by Geoffrey Collins.

The Virtual Boehm Flute may suggest other fingerings for this note.
Fingering legend
How were these results obtained?
Acoustic measurements are available for these flutes -
modern B, modern C, classical C, classical D, classical flared, baroque
Sound clips are available for modern B, classical flared and baroque
To compare flutes, it is easiest to open a separate browser window for each instrument.

Copyright © Academic Press. JSV+ Joe Wolfe, John Smith, John Tann and Neville H. Fletcher, Acoustics of baroque, classical and modern flutes
Revised to include the baroque flute 2001.