In an unenclosed space, all sounds are dissipated in no time. The sound in the open space dissipates rapidly. While listening to music, the sound wave reaches our ears in several ways. Direct sound is the first to arrive. He travels the road in a fraction of a second. The acoustic wave first bounces off the walls, ceiling and floor, then reaches the ears. The acoustic wave is delayed in relation to the direct wave. These sounds are called "first reflections". The wave while bouncing reaches us several times with increasing delay and damping, which floats to a lower and lower sound level. The sound impulse can be divided into three periods: duration of sound rise, duration of sound and its disappearance. The moment when the sound disappears is called the reverberation time. It is determined when the sound level in a room decreases by 60 dB after switching off the equipment, the so-called milestone. The length of reverberation time is determined by many factors, e.g.: volume of a room, number of people staying in it, physical features of the room, e.g. number of furniture, etc. The reverberation time is determined by many factors, e.g.: volume of a room, number of people staying in it, physical features of the room, e.g. the number of furniture, etc.
Sometimes it comes to mind that fidelity to music is possible when the reverberation time is shortened. However, this procedure is not a positive solution. A room that is too dimmed makes the sound unpleasant, unnatural and dry.
Thanks to the conducted research and calculations it is possible to determine how long the reverberation should last in order to be the most suitable for a particular room. For example, in lecture halls, the reverberation time should be relatively small at about 0.2-0.4 seconds, while for churches the reverberation time must be greater and oscillate between 3 and 6 seconds. In houses and apartments, the best reverberation time should vary between 0.6-0.8 seconds. If the reverberation time is too long, it will be difficult to understand speech, but when the reverberation time is too short, the acoustics of the room will be dead, strange and unnatural. Therefore, the aim is to achieve appropriate reverberation time parameters, which is about 2-3 seconds for large rooms, e.g. concert halls, as well as 1-1.5 seconds for smaller halls. Reverberation has several advantages. Increases the acoustic energy in the room and improves the cohesiveness of speech and music.
Multiple reflection of acoustic waves from walls translates into increased acoustic energy, which is most desirable in large theatres, auditoriums, churches, lecture halls or home theatres. An acoustic wave allows you to hear the right sounds, even when you are away from the sound source. This translates into the comfort of listening to a lecture or a concert.
When the reverberation time exceeds 100 ms, an echo effect occurs. A delay time of more than 100 ms makes it possible to distinguish between the two sounds.
Echo is quite a frequently observed phenomenon, e.g. during a walk in the forest. Sounds are reflected from the surface of trees like a wall. The echo effect can also be seen in the mountains. Sounds are reflected from the mountain slopes.