اعادة توليد الصوت المجسم - تسجيل شريط الفيديو - تسجيل الشريط والاسطوانات المجسمة

Stereophonic sound reproduction - Videotape recording - Stereophonic tape and CD recording.. Electronics

Stereophonic sound reproduction

Stereophonic sound is characterized by having a direction and depth just as it happens when we hear a live orchestra performance. This effect is due to the presence of changes in the intensity and phase of the sounds coming from different directions (197). We can get the same result by using two microphones, two amplifiers and two loudspeakers at the same time. Therefore, a person standing on the third corner located at the head of the triangle formed by the two speakers and the same person's location can hear the sound in stereo and imagine that he is watching a live performance.

Stereophonic CDs contain two channels, one right and the other left, located on one groove, and produced by using two microphones for the left and right or directional microphones.
It is known that the stereo needle or pickup can vibrate in two different directions, and its vibration in a certain direction leads to changes in the magnetic field behind the right recording head, while its vibration in the other direction leads to a change in the magnetic field of the left recording coil, after which each output goes to its own amplifier and microphone (198).

197 - Stereophonic sound recording.
198 - Stereophonic sound discs.

As for the recording tape, it contains two or four wires that feed two separate channels, left and right (199). In other words, the recording is made from two separate sources, each of which is amplified separately, while the stereo recording is listened to through two separate amplifiers and microphones.

To obtain good stereo recordings, it is preferable to equip the devices with high fidelity amplifiers, i.e. circuits capable of giving the matching tones without significant distortion over a wide range of oscillations.

Videotape recording

The frequencies associated with photo or television recording are much higher than those used in audio recording only. And they require the tape speed to be very high.

This obstacle is overcome by using recording heads placed at equal distances on the outer circumference of a rotating wheel in front of which the tape, which is 3/4 inch, 1 inch or 2 inch wide, passes, which makes the recording tracks at a specific angle (200).

The speed of the tape depends on the type of recording required and may be 15 inches per second or 7.5 inches per second. There is another type whose actual speed is 75 feet per second.

199 - Dual tracks on stereo recording tape.
200 - Video recording on tape.