Table of Contents
What type of signal is voice?
Normally, voice is transmitted to the human ear by means of an acoustic wave travelling through the air at the speed of sound. A conventional analog telephone transmits sound through a wire as an electrical signal which travels at close to the speed of light.
What is a signal in a speech?
The speech signal, as it emerges from a speaker’s mouth, nose and cheeks, is a one-dimensional function (air pressure) of time. Microphones convert the fluctuating air pressure into electrical signals, voltages or currents, in which form we usually deal with speech signals in speech processing.
What is the difference between audio signal and voice signal?
Voice signals have a rate that ranges from about 4 Kbps when heavily compressed and low quality to 64 Kbps. Audio signals range in rate from 8 Kbps to about 1.3 Mbps for CD quality.
Is voice signal analog or digital?
Difference between the Analog signals and Digital signals
| Analog signals | Digital signals |
|---|---|
| Analog signals produce too much noise. | Digital signals do not produce noise. |
| Examples of analog signals are Human voice, Thermometer, Analog phones etc. | Examples of digital signals are Computers, Digital Phones, Digital pens, etc. |
What are the characteristics of speech signal?
Three important characteristics of speech signal is short time zero crossing, energy and auto correlation. The short time energy and short time zero crossing rates are important properties for detecting the end point of a speech signal analysis.
What is the bandwidth required for voice signal?
The bandwidth allocated for a single voice-frequency transmission channel is usually 4 kHz, including guard bands, allowing a sampling rate of 8 kHz to be used as the basis of the pulse-code modulation system used for the digital PSTN.
What are the three different levels of audio signals?
There are three main audio signal levels: mic level (millivolts), line level (around 1 volt) and speaker level (around 10 volts or more).
Is voice signal continuous?
A continuous signal, such as voice, has a continuous range of amplitudes, and therefore its samples have a continuous amplitude range. In other words, within the finite amplitude range of the signal we find an infinite number of amplitude levels.
How is a speech signal declared to be voiced?
This is accomplished by dividing a speech signal of your choice into short frames and by computing the average power of each frame. The speech in a particular frame is then declared to be voiced if its average power exceeds a threshold level that is chosen by the user. Otherwise it is declared unvoiced.
Is the human voice an analog or digital signal?
Human speech, and everything else you hear, is in analog form, and early telephone systems were analog as well. Analog signals are often depicted as smooth sine waves, but voice and other signals are more complex than that, since they contain many frequencies.
How is a voice signal converted into a bit stream?
To transmit a voice signal, the telephone network equipment first converts it into a stream of bits with a constant rate of 64 Kbps (see section 1.2.1 ). Some video-compression standards convert a video signal into a bit stream with a constant bit rate (CBR). For instance, MPEG1 is a standard for compressing video into a constant bit rate stream.
What should the quality of a voice signal be?
Audio signals range in rate from 8 Kbps to about 1.3 Mbps for CD quality. For the voice or video application to be of an acceptable quality, the network must transmit the bit stream with a short delay and corrupt at most a small fraction of the bits.