acoustics+2

__Acoustics in an Auditorium for 100 people:__ After reading and looking for information of acoustic, I have learned that there are very specific requirements to achieve good acoustic in an auditorium.

these requirements are:

 * There should be adequate loudness in every part of the auditorium, especially in remote seats.
 * The sound energy should be uniformly distributed within the room.
 * Optimum reverberation characteristics should be provided in the auditorium to facilitate whatever function is required.
 * The room should be free from acoustical defects (distinct echoes, flutter echoes, picket fence echo, sound shadowing, room resonance, sound concentrations and excessive reverberation).
 * Background noise and vibration should be sufficiently excluded in order not to interfere in any way with the function of the enclosure.

Adequate Loudness
The problems of providing adequate loudness result mainly from the inverse square law and excessive absorption by the audience attenuating the direct sound before it reaches the listener. This sound loss can be minimised in a number of ways. 
 * The auditorium should be shaped so that the audience is as close to the sound source as possible. In larger auditoria the use of a balcony brings more seats closer to the sound source.
 *  The sound source should be raised as much as is feasible in order to secure a free flow of direct sound to every listener.
 *  The floor on which the audience sits should be properly raked as sound is more readily absorbed when it travels at grazing incidence over the audience. As a general rule, however, the gradient along aisles of sloped auditoria should not be more than 1:8 in the interests of safety. The audience floor of theatres for live performance, especially open or arena stages should be stepped [Tutorial: How to step the floor].
 *  The sound source should be closely and abundantly surrounded by large sound-reflective surfaces in order to increase the sound energy received by the audience. It must be remembered that the dimensions of the reflecting surfaces must be comparable with the sound waves to be reflected. In addition, the reflectors should be positioned in such a way that the time-delay between the direct and reflected sound is as short as possible, preferably not exceeding 30 msec and definitely not more that 80 msec [Tutorial: Positioning reflectors].
 *  The floor area and volume of the auditorium should be kept at a reasonable minimum, thus shortening the sound paths. The following table details recommended Volume-per-seat values for various auditoria.
 * Parallelism between opposite reflective walls, particularly those close to the source, should be avoided in order to eliminate undesirable back reflection and flutter echo.
 * The audience should only be placed in areas which are advantageous to both viewing and listening - generally the two are in agreement. Excessively wide seating areas should be avoided. In addition, aisles should preferably be located at the sides of the auditoria where viewing is restricted, not down the centre where viewing and listening is most favourable.
 * <span style="font-family: Arial,Helvetica;">In addition to reflectors directing sound towards the audience, additional reflectors are often needed to reflect sound back at performers to enhance their ability to hear what is happening on stage.