| Acoustic
Treatment |
A completely bare, empty room will have undesirable acoustics. It
will be very "echoy," with uneven bass. Acoustic room treatment
is the application of various problem-solving materials attached to
the room's surfaces and/or placed within the room.
Acoustic treatments affect the sound at any particular room boundary
in one of three ways. They can:
Absorb sound. Sound striking the surface is absorbed
and not retransmitted to the room.
Diffuse sound. Sound striking the surface bounces
back into the room in all directions.
Reflect sound. Sound striking the surface bounces
back like a billiard ball striking a bumper (or a light ray shining
on a mirror).
How a particular acoustic treatment affects sound will also vary with
the audio frequencies involved (i.e. the pitches of the notes). For
example, a thin acoustic treatment such as lightweight draperies may
abort high frequencies, yet may allow midrange frequencies to be reflected
by the wall behind the draperies.
Bass notes have much longer wavelengths. As the wavelength approaches
the dimensions of the room, resonance becomes the dominate physical
phenomenon governing the room's bass acoustics. Much larger, thicker
absorption materials are needed to treat bass than are needed for
high frequencies. The corners of the room will build up the most bass
energy. In a rectangular "shoebox" shaped room, there will
be eight tri-corners (four at the floor, four at the ceiling) where
you will find the most bass energy building up under steady-state
conditions. So it naturally follows that this is where you would usually
first think to treat the room with bass trapping.
Another aspect of analyzing a room's acoustics is calculating the
room's resonant frequencies. We usually recommend that, when building
a new room, you limit the shape of the room to a simple rectangular
prism (shoebox-like shape). With this shape room, it is easier to
predict the axial, tangential, and oblique modes than if the room
is odd-shaped. However, if you already have an irregularly-shaped
room, we can measure it's resonances with sophisticated computerized
testing equipment..
Above the bass region, room reverberation dominates the room's acoustics.
An overly reverberant room (known as a "live" room) has
unpleasant acoustics. It will be very hard to hear sounds distinctly.
On the flip side, a completely non-reverberant ("dead")
room, will cause an unpleasant "pressure on the ears" feeling,
and will hinder the performance of a high quality audio system.
One particular type of reverberation is called "slap echo."
If you clap your hands once sharply in a room with parallel bare walls,
you will hear slap echo -- a series of rapid distinct echoes. Because
slap echo degrades music reproduction, it is one of the things that
we seek to minimize when treating a room acoustically.
Tip: Most people are highly sensitive to the reverberation characteristics
of a room. Even if you don't listen to music in a particular room,
you may which to consider room acoustics in its construction. For
example, a large, overly-live living room, family room, or dining
room will not invite relaxed conversation.
Any listening room, whether for live music or reproduced sound, can
be substantially improved with a comprehensive acoustic treatment
design. We have used all sorts of approaches, many of which can be
retrofitted to an existing room.
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