A good listening room should satisfy some basic acoustic conditions, mainly the sound insulation of the room, the reverberation time should be appropriate and the harmful acoustic phenomena in the room should be suppressed. As a listening room for monitoring audio equipment and sound recordings, attention should also be paid to the standardization of indoor acoustic conditions to ensure the reliability and consistency of the audit results.
A qualified listening room requires the following three elements:
1, sound insulation performance is better
Wave-absorbing cotton
The sound insulation performance is good, and the listening room has no or few sounds including noise and music in and out of the outside space. This is the most basic condition required for HI-FI playback. This condition is equivalent to the signal to noise ratio of the amplifier. The room is soundproof, and the external noise is not easy to enter the room to interfere with listening. The external noise here includes two aspects: one refers to the external environmental noise; the other refers to the noise from the neighbors, the upstairs and downstairs, and the other rooms from the same room. The "meaningful" noise generated by the latter, such as the sound of movies and TV in the TV, the sound of the children's piano, can be "understood" by us, not only interferes with the sound of music, but also distracts us from listening to music more than normal noise. Attention to time reduces the understanding of music. Therefore, it is necessary to pay attention to the sound insulation of the external environment noise, and also attach great importance to the sound insulation between indoor rooms.
A room with good sound insulation is not easily interfered by external noise, and it is not easy to interfere with the normal rest or work of the neighbors and other people in the family. It is convenient for people, that is, it is convenient for themselves, and they are all happy. It’s so good to enjoy great music.
More importantly, in a room with a high “signal-to-noise ratioâ€, it is easier to hear the subtle parts of the music and get more information. This part of the sound is often very subtle, sometimes like “MSGâ€. Not very different. Low noise is equivalent to increasing the dynamic range of music, which is one of the important conditions for realizing the sound. This is a condition that cannot be ignored for the playback of SACD and DVD-Audio, which have a particularly high signal-to-noise ratio. Relatively speaking, in a low-noise room, you can listen at a lower volume, which helps to reduce the distortion of the audio equipment and increase its power reserve.
In short, a good listening room, sound insulation performance is very important.
2, moderate reverberation
Playing sounds in different rooms, their sound performance is often different. Some are nice, some are turbid, others are "dry". These three types of space can be found in the average family. You may wish to experience it yourself, take a portable radio and listen to the language program (also listen to music programs). Then listen to the bedroom, the bathroom and the semi-exposed balcony, you can immediately feel the above three different effects. The main reason for the above differences is that the three types of spaces absorb different degrees of sound. In acoustic terms, it is "reverberation (time)". In fact, strictly speaking, any object will absorb sound waves, the difference is that the degree of sound absorption is different. Hard walls and smooth tiles absorb little sound. The unabsorbed part of the sound is reflected back and continues to reflect. It takes a while for the sound source to stop sounding, and we can't hear it until the sound is mostly absorbed. This is the case with the bathroom. The situation on the balcony is completely opposite. After the sound goes out through the semi-exposed space, it does not return. Therefore, after stopping the radio, the sound disappears quickly. The situation of the bedroom is between the above two cases, because it has more soft cotton fabrics and curtains, etc., the ability to absorb sound is in the middle.
The room absorbs the sound strongly, and the sound decays quickly after the sound source stops. On the contrary, the absorption of sound in the room is weak, and the attenuation of the sound is slow. The decay process of the above sound is generally referred to as "reverberation (process)". The strength of the reverb is indicated by the "reverberation time". It refers to the time required for the sound source to stop sounding after it has reached a steady state (usually 0.1-0.2 seconds), and the sound is attenuated by 60db indoors. In a fully enclosed washroom, the reverberation time depends on its size, usually up to several seconds. In the average bedroom, it is about a range of 0.5 seconds. On the balcony, the reverberation time is almost zero.
It can be seen from the above that the length of the reverberation time reflects the intensity of the room's absorption of sound. Strong sound absorption, short reverberation time, and vice versa. At the same time, we also know that the reverberation time has a significant impact on the sound quality, too long or too short is not good. Obviously, there is a compromised reverberation time value (or a range) called the "best reverberation time." The best reverberation time for a large concert hall is around 1.5 seconds, the best mix of home listening rooms. The time is usually around 0.3-0.5 seconds. Appropriate reverberation time can make the sound full, clear, and bright, and the output power of the amplifier can be smaller, or it can help to increase its power reserve. Coupled with the same benefits of improved sound insulation, it is more advantageous for replaying dynamic music programs. In short, the reverberation time is the sound quality of the room.
3. Suppress harmful acoustic phenomena
When playing indoors, in addition to directly hearing the direct sound from the speaker, I also heard the direct reflection of the reflected sound coming back from the wall. The vast majority of the home listening room is a rectangular parallelepiped with three pairs of parallel walls. The two reflected sounds that may be generated by each pair of parallel walls are particularly harmful to sound quality and should be avoided as much as possible.
1, standing wave
This is the natural resonance of the sound reflected between a pair of parallel wall surfaces. Therefore, at a fixed location in the room, the sound pressure of some frequencies is increased due to the same resonant frequency as the room, and the sound pressure at other frequencies is small, even Can not hear, this phenomenon is called the generation of standing waves. The standing waves in the actual room are not limited to parallel walls, but the standing waves generated between the parallel walls have the greatest influence. Due to the presence of standing waves in the room, the frequency response of the speaker whose frequency response is fairly even and flat, the frequency response at the listening point also becomes uneven. The influence of the standing wave mainly occurs in the low frequency band, and the listening room of the room is always small, so the sound dyeing of the standing wave cannot be ignored.
2, vibrating echo
Another unwanted reflection that may be produced between parallel walls is the tremor echo, which is a series of short pulsating echoes. If the sound is reflected back and forth between the walls many times without attenuating, the same repeated reverberation echo will be heard. This kind of echo can impair the clarity of the playback. It is usually possible to check the presence of a vibrating echo in the room by clapping the hand. Of course, you should listen to it in a quieter environment. If the environment is noisy, it may not be easy to detect. The usual listening rooms have noticed that the sound absorbing material is to be laid on the wall, so the tremor echo is not easy to occur, especially when the room is small. Relatively speaking, the frequency of standing waves is low, and the wall absorption is often not very effective, which is the biggest problem affecting the sound quality of the room!
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