The home theater pursues the audio-visual effects of the cinema, and the subjective requirements of various listening sensations are similar to the subjective requirements of the cinema. However, in order to get good sound, you must have a good environment. The realization of the entire audio system function is composed of many links: including recording production, CD player, power amplifier, speaker system and human feelings. The sound from the speaker system must reach the person's ear and must pass through the room, so the room is an important part of the sound system. A good indoor acoustic environment is essential for achieving the ideal listening experience in a home theater. In this regard, many enthusiasts have the feeling of "three-point equipment, seven-point environment".
1. Sound field characteristics
The sound field of 2 times the wavelength of the large dry is called the far field, and the sound field of the wavelength less than 2 times is called the near field. In a general home theater, the volume of the listening room is not large enough to be called the near field, the near-field sound shadow area becomes smaller, and the sound field distribution and the sound propagation law are very different from the far field. Since the wavelength of the low-frequency sound is long, in a small-sized room (compared to the wavelength), the bass cannot be reproduced well, and the original sound field is certainly uneven. Therefore, the home theater sound field design should first focus on the processing of low-frequency sound to ensure the uniformity of the indoor sound field.
2, frequency response
The human audible sound is in the range of 20 Hz to 20 kHz. It is not difficult to achieve the frequency response of the CD player, the power amplifier and the speaker system in this range. But the room is also a resonator and has its resonant frequency. Due to the different three-dimensional geometrical dimensions of the room, the resonance frequency is not one, but many, distributed in the entire frequency band. If the density of the vibration frequency is relatively large and evenly distributed, the frequency response of the whole room is relatively straight, otherwise There will be many peaks and valleys. If there is no frequency in the room's simple vibration spectrum, even if the speaker system emits a sound of this frequency, it will not stimulate the room's air to vibrate accordingly, and we can't hear it.
3, reverberation time
Reverberation is the result of the sound in the room being continuously reflected by the interface. Reverberation can increase the sound in the room, and the early sound reflection sound is mixed with the direct sound, resulting in sound.
The sound level is increased. However, the audio and audio of the audio are deviated, resulting in inaccurate audio sounds, affecting the clarity of the sound. Reverberation time is an important parameter that affects the sound quality of the theater. Reverberation time control can improve speech clarity and tone fullness. It is impossible for any room to have no reverberation. The sound we hear is the result of the reverberation of the room and the reverberation of the source. If the reverberation time of the room is too long, the listening effect will be affected.
The sound quality indicator refers not only to the average reverberation time, but also to the reverberation time of the six octave center frequencies. According to the "Standards for Reverberation Time Measurement of Halls" CBJ 76-84 Chapter III Measurement Method 3.1.1 The frequency selected for measuring reverberation time should not be less than the following 6 octave center frequencies: 125. 250,500, 1K, 2K, 4K (Hz), if necessary, increase the frequency to the center frequency of 1/3 octave. The frequency should be selected in accordance with the current national standard "Common Frequency in Acoustic Measurement" GB3240-820.
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