[Openal] Hear sounds in a certain distance range only

[Daniel PEACOCK]

Hi,

There are a couple of options ...

a) The easiest method is to use the Linear Distance (Clamped) Model.  This
model guarantees that a sound will fade from full volume at Reference
Distance to silence at Maximum Distance.  See
http://connect.creativelabs.com/openal/Documentation/OpenAL%201.1%20Specification.htm#_Toc199835867
 for more details.

b) If you want to use the Inverse Distance (Clamped) Model (the default
model) you'll need to decide what amount of attenuation is 'close enough'
to silence, e.g. -30dB, -60dB, -90dB or -100dB etc ... and compute the
distance which gives this amount of attenuation, e.g. ...

NOTE : The problem with this distance model is that sounds take a long time
to get very quiet due to the exponential roll-off, eg ...

Say your target is -60dB, and reference Distance is 2, rolloff factor is 1

-60dB == 0.001 linear gain.

Inverse Distance Clamped model ...

gain = Reference_Distance / (Reference_Distance + RollOff_Factor *
(Distance - Reference_Distance))

As RollOff_Factor is 1.0 this simplifies to ...

gain = Reference_Distance / Distance

Distance = Reference_Distance / gain

Distance  = 2 / 0.001

Distance = 2000

-60dB is very quiet so you could increase this to say -30dB (which might be
OK if you have lots of other sounds playing at the same time).  -30dB ==
0.0316 linear gain which is achieved at a distance of 63.

Dan
Creative Labs (UK) Ltd.

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             Andreas Bednarek                                              
             <andris at seznam.cz                                             
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                                       [Openal] Hear sounds in a certain   
                                       distance range only                 
             04/19/2009 01:05                                              
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Hello, please is there a property to set for a sound source if I want it to
be hearable in a certain distance range only?

Thanks
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