have more modes than the preceding one). Other systems to determine correct room ratios have more recently been developed. Reverberation of the room After determining the best dimensions of the room, using the modal density criteria, the next step is to find the correct reverberation time. The most appropriate reverberation time depends on the use of the room. Times about 1.5 to 2 seconds are needed for opera theaters and concert halls. For broadcasting and recording studios and conference rooms, values under one second are frequently used. The recommended reverberation time is always a function of the volume of the room. Several authors give their recommendations A good approximation for broadcasting studios and conference rooms is: TR[1 kHz] = [0.4 log (V+62)] – 0.38 seconds, with V=volume of the room in m3. Ideally, the RT60 should have about the same value at all frequencies from 30 to 12,000 Hz. To get the desired RT60, several acoustics materials can be used as described in several books. A valuable simplification of the task was proposed by Oscar Bonello in 1979. It consists of using standard acoustic panels of 1 m2 hung from the walls of the room (only if the panels are parallel). These panels use a combination of three Helmholtz resonators and a wooden resonant panel. This system gives a large acoustic absorption at low frequencies (under 500 Hz) and reduces at high frequencies to compensate for the typical absorption by people, lateral surfaces, ceilings, etc. Acoustic space is an acoustic environment in which sound can be heard by an observer. The term acoustic space was first mentioned by Marshall McLuhan, a professor and a philosopher. Nature of acoustics In reality, there are some properties of acoustics that affect the acoustic space. These properties can either improve the quality of the sound or interfere with the sound. Reflection is the change in direction of a wave when it hits an object. Many acoustic engineers took advantage from this. It is used for interior designs, either use reflections for benefits or eliminates the reflections. The sound waves usually reflect off the wall and interfere with other sound waves that are generated later. To prevent sound waves reflecting directly to the receiver, a diffusor is introduced. A diffusor has different depths in it, causing the sound to scatter in random directions evenly. It changes the disturbing echo of the sound into a mild