Digital Signal Processing Reference
In-Depth Information
0,0150
0,0125
0,0100
0,0075
0,0050
0,0025
0,0000
-0,0025
-0,0050
-0,0075
-0,0100
-0,0125
Time domain
0
50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950
ms
1. Harmonische (Grundton; ca.123 Hz)
2. Harmonische (1. Oberton)
6. Harmonische
9. Harmonische
12. Harmonische
1. Harmonic (123 Hz)
2. Harmonic
6. Harmonic
9. Harmonic
12. Harmonic
0,0008
0,0007
0,0006
0,0005
0,0004
0,0003
0,0002
0,0001
0,0000
Frequency domain
0
250
500
750
1000
1250
1500
1750
2000
Hz
Illustration 57:
Sound as the superimposition of various different tones
Extract from a jazz recording (Rolf Ericson Quartet). At this moment trumpet and piano are playing. While
the time domain betrays little of the near-periodic character of the music, the situation is quite different in
the case of the frequency domain. The lines speak an unambiguous language. However, which lines belong
together? In addition the spectrum does not contain any information as to when certain tones/sounds
within the period of time under consideration were present. From the "width" of the lines, however, conclu-
sions can be drawn as far as the length of these notes/sounds is concerned (
UP
!). In this connection note
once more Illustration 45 and Illustration 55.
We can now continue with simple experiments using our proven method. Thus, we now
use a microphone as a "sensor" - as the source of the electrical signal.
The human ear perceives an acoustic signal as a tone or a sound if it succeeds in allocating
it more or less clearly to a particular frequency. In addition, the signal is felt to be
harmonic if all the frequencies are in a particular relationship to each other (they are
equidistant from each other). As a result of the
UP
, this clear frequency allocation is as a
only possible if the signal is repeated in a similar way over a longer period of time within
the time segment observed.
