Introducing the Acoustic Ramp™ Diffuser

As some of you already know, I invented a new type of number-theoretical diffuser a while ago and I have been working on developing it into a product and filing the necessary patent applications.  It’s called the Acoustic Ramp™ because it is wedge shaped.  The diffuser became my master’s thesis for my degree work at the University of Massachusetts in Lowell in Sound Recording Technology.  The degree that I will earn is called a Master’s of Music in Sound Recording Technology (M.M. S.R.T.) and will hopefully make it easier to get a job that pays the bills!

This past Saturday 7/30/2011 I spent the day running a series of tests on the diffuser and comparing its performance to that of a flat reflector.  Essentially what I am trying to show is how much better the back wall of a control room would be if it had an array of my Acoustic Ramp™ diffusers and wasn’t a flat wall.  When sound hits a flat wall it bounces back, a lot like a rubber ball might bounce.  The problem is that the sound bouncing off the wall interferes with the sound going towards the wall and causes problems like comb filtering, flutter echo and bass buildup. One option for handling the problem is to absorb all of the sound hitting the wall and preventing it from reflecting.  This works, but really changes the sound of the room, deadening the frequency response and creating an unnatural ambiance. The other option is to use diffusion to reflect the sound in many directions and to prevent the sound bouncing back in only one direction.

Testing the Acoustic Ramp

Testing the Acoustic Ramp at U. Mass Lowell's Concert Hall

Testing a diffuser is actually pretty complicated and involved, but in a nutshell the process is as follows:

Shoot an impulse burst of sound at the diffuser and then record what bounces back every 5 degrees in the semi-circle around the diffuser.

The white tape in the picture shows the test points where I placed the microphone. The first test point is at 0 degrees directly underneath the speaker.  This test point simulates what a listener might hear if they were sitting directly in front of the speaker and the sound went past them and hit the back wall of the control room and then bounced back.  A flat wall would reflect a sound very similar to what was coming out of the speaker, essentially an echo that hasn’t been greatly changed. A diffuser should have multiple smaller echoes spread out over time with seriously reduced sound pressure. This is what the 0 Degrees test results look like:

Flat Reflector vs. Acoustic Ramp

Diagram showing the difference between sound reflecting of a flat reflector and sound being diffused by the Acoustic Ramp

As you can see from the diagram, the large reflection in the top response is changed into a series of three smaller reflections  and greatly attenuated (reduced) amplitude when diffused by the Acoustic Ramp.  The reflection is spread across time and diminished greatly in amplitude.

Hurray! It Works!

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