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<H4><A name=_dx_sound_cones_dxaudio></A>Sound Cones</H4>
<P>A sound with no orientation has the same amplitude at a given distance in all 
directions. A sound with an orientation is loudest in the direction of 
orientation. The model that describes the loudness of the oriented sound is 
called a sound cone. Sound cones are made up of an inside (or inner) cone and an 
outside (or outer) cone. </P>
<P>At any angle within the inner cone, the volume of the sound is just what it 
would be if there were no cone, after taking into account the basic volume of 
the buffer, the distance from the listener, the listener's orientation, and so 
on. </P>
<P>At any angle outside the outer cone, the normal volume is attenuated by a 
factor set by the application. The outside cone volume is expressed in 
hundredths of decibels and is a negative value, because it represents 
attenuation from the default volume of 0.</P>
<P>Between the inner and outer cones is a zone of transition from the inside 
volume to the outside volume. The volume decreases as the angle increases.</P>
<P>The following illustration shows the concept of sound cones.</P>
<P><IMG alt="" border=0 
src="http://www.msdn.microsoft.com/library/psdk/directx/dx8_c/hh/directx8_c/images/soundcon.gif"></P>
<P>Every 3-D sound buffer has a sound cone, but by default a buffer behaves like 
an omnidirectional sound source, because the outside volume is not attenuated, 
and the inside and outside cone angles are 360 degrees. Unless the application 
changes these values, the sound does not have any apparent orientation.</P>
<P>Designing sound cones properly can add dramatic effects to your application. 
For example, you could position a sound source in the center of a room, setting 
its orientation toward an open door in a hallway. Then set the angle of the 
inside cone so that it extends to the width of the doorway, make the outside 
cone a bit wider, and set the outside cone volume to inaudible. A listener 
moving along the hallway will begin to hear the sound only when near the 
doorway, and the sound will be loudest as the listener passes in front of the 
open door.</P></FONT></DIV></BODY></HTML>