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Extraction of Pitch from the Trachea

IP.com Disclosure Number: IPCOM000094976D
Original Publication Date: 1965-Jul-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Peckels, J: AUTHOR [+2]

Abstract

The method extracts the pitch of a speech, i.e., fundamental frequency, from the trachea. An accelerometer is used as a transducer instead of a microphone. Advantages result from such use. The accelerometer has flat frequency response down to 5 c/s, thus giving an excellent frequency response in the pitch frequency range of 60-250 c/s. The accelerometer is also highly insensitive to environmental speech and noise. The signal noise ratio is very good. When using a microphone, it is difficult to have a good low-frequency response. The ratio signal to noise is low, even with a good isolation at the throat to avoid environmental noises or speech of the talker itself.

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Extraction of Pitch from the Trachea

The method extracts the pitch of a speech, i.e., fundamental frequency, from the trachea. An accelerometer is used as a transducer instead of a microphone. Advantages result from such use. The accelerometer has flat frequency response down to 5 c/s, thus giving an excellent frequency response in the pitch frequency range of 60-250 c/s. The accelerometer is also highly insensitive to environmental speech and noise. The signal noise ratio is very good.

When using a microphone, it is difficult to have a good low-frequency response. The ratio signal to noise is low, even with a good isolation at the throat to avoid environmental noises or speech of the talker itself.

Accelerometer 1 is closely coupled to the skin on the throat in a region near the vocal cords. The electrical output is proportional to the magnitude of the acceleration and translates the vocal cord excitation function with high fidelity and, thus, the information about pitch. The output is amplified by 2 and applied to a peak detector and a differentiating circuit. Capacitor 4 is charged through the base-emitter diode of transistor 5. A switch selects an adequate time constant determined by capacitor 4 and resistor 3, i.e., type of voice. Resistor 6 is modified by the switch to always insure the same output level.

The first stage A detects negative peaks of the input waveform. The second stage B is identical to the first one but detects positive pulses because the w...