APPLIED ACOUSTICS SYSTEMS ULTRA ANALOG Instrukcja Użytkownika Pobierz pdf (Strona 29)

4.2 The Edit View 29

Formant Filter

Amplitude (dB)

Frequency (Hz)

F1 F2 F3

Male Voice

Female Voice

Formant Frequencies

Figure 14: Frequency response of the formant ﬁlter.

The formant ﬁlter reproduces the ﬁltering effect of the vocal tract in the human voice. By

changing the position of the tongue, the opening of the mouth and opening or closing the nasal

cavities one can change the ﬁlter applied to the glottal signal and thus produce the different vowels.

Measurements have shown that this ﬁlter can be modeled by three peaking EQ ﬁlters corresponding

to the three main cavities of the vocal tract as shown in Figure 14 and also known as formants. By

moving the parameters of these three ﬁlters (frequency, amplitude and Q-factor) one can cycle

between all the vowels. The effect of the Frequency knob on the formant ﬁlter is to offset all the

formants by the same factor and it is used to switch between male voice (left position), female

voice (center) and child (right position). The Resonance knob is used to cycle between vowels.

Note that changing these parameters can be automated by using the different modulation signals.

Filter Drive

As seen in the preceding sections, some ﬁlters can boost the signal in some regions of the spectrum.

Theoretically, with a high Q-factor the ampliﬁcation can reach up to 50dB, but in real life, electronic

components saturate before this level is reached and saturation is introduced in the signal. In other

words, the output signal of a circuit can raise linearly up to a certain value but then begins to raise

more slowly up to a value where the output is clipped to the maximum output value allowed by

the circuit. This effect is typical of the sound signature of vintage circuits and is implemented in

Ultra Analog VA through the Drive control as shown in Figure 15. There are 6 different saturation

patterns implemented, the three ﬁrst being symmetrical, meaning that the saturation is the same

for positive and negative values of the signal while for the three remaining the distortion pattern

applied is not the same for positive and negative values of the signal.

The distortion algorithms are selected with the Drive drop-down menu and are numbered from

1 2 ... 24 25 26 27 28 29 30 31 32 33 34 ... 65 66

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