Basic knowledge of sound

The sound in movies refers to the three major sound elements of human voice, various sounds, and music, which form the auditory impression. We must understand some basic knowledge of sound. Pitch: The pitch of a sound is determined by its vibration frequency. If the frequency is fast, the pitch will be high; if the frequency is slow, the pitch will be low. Volume: refers to the intensity of the sound, determined by the amplitude of the sound wave. If the amplitude is large, the sound will be strong, and vice versa. Timbre: The color of the sound, also known as the timbre and timbre quality. It is also an important attribute of sound. Reverberation: In a certain relatively closed space, sound will last for a period of time and then disappear due to multiple reflections, which is called reverberation. Foley: Use artificial methods to simulate various sounds required in the film. Spatial sense of sound: Different spatial colors are caused by different reverberation times when sound propagates in different spaces. Sense of sound environment: Through different typical sounds, the audience can have a sense of the environment they are in. Three-dimensional sense of sound: Due to the different positions of various sound emitters and different distances from the listener, changes in the intensity difference, time difference, reverberation and other factors of the sound produced allow the listener to determine the relative position and specific orientation of the sound emitters. . The sense of movement of sound; due to the movement of the sound source, changes in volume, pitch, etc., as well as changes in position and direction, etc. will occur. When movement is slow, change is also slow. In film recording, various recording methods must be used to process and process the sound to create a real sense of space, environment, three-dimensionality, movement, etc.

1. Several stages of the development of stereo technology

Around 1881, the French conducted experiments on the binaural effect of telephone lines and sent theater programs through two channels. Go to the user's home and listen with two-channel headphones. Later, the United States also experimented with binaural telephones. These may be called binaural experimental phases. By 1920, British Columbia Records recorded three-channel left-center-right stereo records. In 1926, the British BBC Broadcasting Company began to broadcast stereo programs on AM stations. Stereo movies were introduced in 1937. By the mid-1950s, stereo program tapes began to be published in large quantities. By the 1960s, the United States had perfected stereo broadcasting and established standards. About 300 radio stations across the United States use the standards developed to broadcast. This stage can be called the practical and application stage. In the next 30 years, stereo technology developed rapidly, forming a stage where various stereo systems competed.

2. The simple principle of stereophonic sound

The playback effect of stereophonic sound is to use two or more channels to simulate the orientation of the actual sound source, and the composition is the same as the actual sound source space. The auditory effect of relatively close positions gives a sense of expansion, distribution and width of each sound source. Improved sound fidelity and clarity, making the sound appear layered and present. Allowing listeners to enjoy perfect tone and sound. The biggest feature of stereo sound is high fidelity.

3. Dolby Optical Stereo System

Dolby Optical Stereo is a 35mm movie stereo system, which is a quasi-four-sound system, that is, a 4-2-4 system. When a Dolby optical stereo film is shown in a theater, the three channels are played by three sets of left, center, and right speakers behind the screen and another ambient speaker installed in the auditorium. When shown in ordinary theaters, it can also produce a mono sound effect, and the film can be used simultaneously. This kind of compatibility is not available in other stereo systems.