GOOD HEARING CONDITIONS,

 GOOD HEARING CONDITIONS

In order to have good hearing conditions in any space, whether it be a courtroom, a church, a lecture room, an outdoor theatre or even a living room, it is essential that four basic requirements be met:

 (1) adequate loudness of the sounds to be heard;

 (2) good distribution of the sounds to be heard;

 (3) proper blending good of the sounds with adequate separation for good articulation of Loudness and Distribution.

When sound is radiated from a source in free field, the spherical sound wave moves at about 1,100 ft. per second.

 The energy is spread over a sphere of in-creasing area, and the intensity decreases inversely to the square decreases inversely to the square of the distance. 

When an audience is placed in front of a source

(e.g., a person speaking), the conditions found in a free field do not exist. If the person talking is at almost the same level as the audience, there is an additional loss of intensity as the sound grazes over the people seated in

the audience. 

This is especially important when the audience is on level ground (see ig. 1). The ancient Greeks and Romans understood this very well they built their theaters on steep hillsides in quiet locations (fig. 2) and found that, with the audience placed at a very steep angle, conditions were almost as good as in a free field.

 An alternative is to raise the source of sound high above the audience, but this is not usually convenient. A more satisfactory arrangement is to let the ceiling of the room act as a sound mirror, bringing reflected sound down on top of the audience to reinforce the direct sound. In most auditoriums more sound energy is actually received from

the ceiling than directly from the source of sound. 

The ceiling is the most important surface in the room in assuring adequate loudness and good distribution. A ceiling in any room where hearing conditions for an audience are to be good must always be hard and sound reflecting, never sound absorbing.

There is much misunderstanding of this point.

It is obvious that a listener must be seated so that he can

see" the ceiling if he is to receive useful reflections from it.

If he is seated under a deep balcony, he often will not receive these reflections and will get only the direct sound which has grazed over the sound-absorbing audience ahead of him.

The undersurface of a balcony should always slope up toward the stage, giving the people seated on the main floor a view of a large area. 

ACOUSTIC ENVIRONMENT

Range of sound" 

The table shows that the range of Sounds that's must be tolerated by the ear is enormous, externding from a thereshold value of 1 arbitrary unit to for a faint sound that can Just be detected to 100,000,,000,000,000 unit for a very loud sound 

Intensity of Sound