Difference between digital and analog
The sound is analog. And sound is the vibration of the air. How is this sound vibration transmitted?
For example, when a stone is thrown into a calm water surface, the ripples spread around it, but if
Cut in the direction of the waves and look at the cut end, the waveform is as shown in Fig.1.
Air waves spread from the point where sound is emitted even in air. Although invisible to the eye, it has a
similar waveform. This is the analog waveform of sound.
Therefore, although it is digital, when such a sound waveform is recorded or communicated by phone or wireless, as
shown in Fig. 2, the change in the analog waveform is electrically replaced with a series of numerical values according to a certain promise. ..
When recording or communicating, if you handle it as analog, it is easy for noise to enter and the sound quality to deteriorate, but when trying
the waveform of the sound as digital = numerical data, you can eliminate that worry and
maintain a certain quality. You can do various processing while maintaining it.
(2) What is convenient when it is digital
Digital audio signals are convenient because they can be recorded and edited using a personal computer, for example.
In addition, 74 minutes of music can be recorded on a CD with a diameter of only 12 cm, and through digital compression processing
, music of the same length can be recorded on an MD with a smaller diameter.
Since digital signals can be compressed in this way, it is also convenient for storing large amounts of information.
Not only sound, but also video signals with a higher amount of information can be recorded and communicated at high speed through the use of compression technology.
Especially in communication, a two-way digital multiplex communication can be realized communicating multiple pieces of information with a single wire.
In addition to electrical signals, laser light can also be used for optical communication, making communication possible at extremely high speeds.
(3) What is the sampling frequency?
Digital signals are processed at predetermined fixed time intervals.
The sample rate (sample rate) indicates how many times a second is processed and is expressed as Fs or fs.
The sampling frequency unit is Hz (Hertz), and the
44.1 kHz (kilohertz) sampling rate means 44,100 pieces of data are processed per second.
(K represents 1000 times)
AD conversion converts a continuous analog signal into a digital signal,
measures the size of the signal at each moment determined by the sampling frequency (sampling) and converts
the result in a binary number (quantization).
On the other hand, DA conversion converts a digital signal into an analog signal,
It reads the digital signal in the sample rate time interval and connects it smoothly.
Since digital signals can be reproduced up to half the sampling frequency, how much
The higher the sample rate, the higher the playable frequency and the better the sound quality.
In familiar areas, 44.1 kHz is used for CD, and 48 kHz is used for DAT and B modes of satellite transmission.
In addition, recent professional equipment uses high sampling frequencies (high sampling), such as 88.2 kHz and 96 kHz,
and are designed to faithfully reproduce even higher frequency sounds to improve sound quality.
