# Binaural measurement + how exactly does REW process L/R microphone input signals?



## Ge0 (Nov 6, 2007)

I've followed / used the work of Dr. Earl Geddes to tune automotive audio systems professionally to down right spooky / lifelike results. I used specialized commercially available hardware and software to achieve this. But who can afford this if they want to apply similar principles at home??? Then I stumbled across the promise of REW while casually browsing. I have the right equipment / processing power. I wonder if I could apply the same principles to home audio?

In a nut shell this would involve using a binaural in-ear microphone set or a binaural microphone dummy head to collect data. One signal is measured from each ear, the data set is summed, then averaged. The user is encouraged to move about freely while measuring (as you would do naturally while listening) which is also averaged. The end purpose is to capture the "sound energy" in the general vicinity of your head. This adds more complexity. However, I find the results superior to what I have found using the conventional measurement input from a single point source located in a fixed position. 

Anyway, I was wondering if REW was versatile enough for me to explore binaural input capture. I notice during level checks and such REW appears to support L/R microphone measurement input. But no further mention about this in any threads I searched. When you measure a result just pops out?

My question. How is this result derived when using a stereo mic or binaural headset? 

Do you have any thoughts about how I can come close to achieving what I am trying to experiment with through various software settings? 

Sorry if what I ask is confusing. I'm also confused. Please feel free to talk and ask for clarification.

Ge0


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## AudiocRaver (Jun 6, 2012)

Ge0 said:


> I've followed / used the work of Dr. Earl Geddes to tune automotive audio systems professionally to down right spooky / lifelike results. I used specialized commercially available hardware and software to achieve this. But who can afford this if they want to apply similar principles at home??? Then I stumbled across the promise of REW while casually browsing. I have the right equipment / processing power. I wonder if I could apply the same principles to home audio?
> 
> In a nut shell this would involve using a binaural in-ear microphone set or a binaural microphone dummy head to collect data. One signal is measured from each ear, the data set is summed, then averaged. The user is encouraged to move about freely while measuring (as you would do naturally while listening) which is also averaged. The end purpose is to capture the "sound energy" in the general vicinity of your head. This adds more complexity. However, I find the results superior to what I have found using the conventional measurement input from a single point source located in a fixed position.
> 
> ...


REW allows you to select either L or R input from a 2-channel audio interface. I prefer to use a small external mixer/mic preamp and switch rather than mess with the input selection, much faster (plus drivers do not always behave when switching back & forth in REW or any other audio program). The measurements would be taken one at a time, as you suggest. Summing and averaging are both possible under Graph Controls (gear at upper right) for the All SPL panel.

REW mainly uses a measurement sweep from 15 to 22,000 Hz for each measurement. This includes timing/phase data and is not conducive to "moving around while measuring." You must be doing that with pink noise and an RTA. REW has an RTA mode, too, not discussed or used as much but it will work for your application. The "moving mic measurement" method is a great way to get averaged data with an RTA, but there is no time/phase information captured, which can also be useful.


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## Gusss (Feb 7, 2015)

if you want to measure your HRTF its probably doable with rew - but remember each of your pinnae are different so I dont think you should sum it ?


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## Ge0 (Nov 6, 2007)

Sorry I opened this topic and appeared to drop of the map. No excuses. I travel a lot and lead a busy life.

Let me clarify. Phase and timing taken from primary listening position using point source mic and REW sine sweep. This helps establish proper crossover points of multi-driver active system. Driver positions are not 100% symetrical and in the same plane. Timing used to make subtle corrections.

Use pink noise with 1/12th octave RTA to adjust frequency response to my desired target curve.

When I said move around I did not mean get up and walk around. I meant let your head move freely while making mesurements in the listening position. You don't need to freeze while taking a measurement.

Hope this explains my idea better. Will try using REW math functions to process individual plots.

Ge0


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