Characterising the room.
Characterising the behaviour of the room is the first step towards your understanding of
your listening room’s contribution to the audio system. Follow the simple procedure
below to obtain a better understanding where changes could be made in order realise
improvements.
1. Record data of the room dimensions onto a simple floor plan. Graph paper can assist
you with this.
2. Apply the data (dimensions) to the formula
3. Make a record of the predicted standing wave frequency characteristic for each
parallel wall dimension of the room.
4. Verify your predictions using the Wilson Benesch test CD which has a number of
fixed frequency tests and swept frequencies. Use these to verify and back up your
prdictions.
Note 1 big differences in percieved and calculated values will indicate an error
Note 2 If the predicted frequency matches with the perceptible increase in output in the
room this has verified your prediction.
Note 3 The listening tests should be taken whilst seated in the main listening position.
Evaluate the data and look for errors.
5. Assess whether changes should be made and what can be changed in order to
overcome any dramatic and clearly in accurate increase in sound pressure levels.
Middle and High Frequency Room Characteristics
The middle and high frequncies are affected more by room contents rather than room
shape. The “sound” of a room is described by the surfaces and how they
reflect, absorb
or
diffuse
the acoustic energy. Like all energy acoustic energy cannot be destroyed it can
only be converted into something else or refected. The shape of the surface will
determine how it is reflected and the material will determine whether it is absorbed. All
rooms have a particular sound and to appreciate what influences are present in your
room you should be aware of how the objects in your room will respond to sound.
Sound waves behave in the same way as light waves or "rays" and so imagine the driver
to be a flood light.
Reflection:
acoustic energy is not converted but reflected in an orderly, predictable
fashion.
Diffusion:
acoustic energy is dispersed in a random and or disordered fashion.
Absorption:
acoustic energy is converted into kinetic energy or heat. All or a majority of
the sound energy is "soaked up" or disposed of by the object surface or room boundary.
Summary of Contents for Act
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