Acoustic Room calibration in a semi anechoic environment

asb

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May 5, 2024
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Hello everyone!

My name is Victor, passionated about DYI loudspeakers and I started a side project related to acoustic. More specifically, I built a semi anechoic environment in Berlin.
I have an engineering background by I've never learnt anything related to acoustic. It's why I created this channel to get your help on a problematic I am facing with regarding my project:

Context

- I just built a semi anechoic environment in Berlin
- I use REW to proceed to my measurements.
- My semi anechoic environment works well. But I just have one reflection coming from the floor.
- I would like to minimize this problematic by modifying my calibration settings in REW.

Problematic

- I would like to create my own acoustic calibration from the room by throwing a sweep in my room using the most linear speaker i can find.
- I would like to use this measurement as an acoustic calibration for processing to my future measurement in the room.
- However REW does not provide the functionality of adding a 3rd calibration file on top of the calibration made from the audio interface and the microphone.

How to solve this problem?

- If we take a look at the calibration file made with the audio interface (.cal file format), we can see the data of the frequency response.
- So what I would like to do is:
- Make a measurement in my room with the most linear speaker i can find.
- Export the frequency response data available on the .txt file.
- Swap the frequency response data from the calibration file by the frequency response data I got with the test I did in my room.

So at the end, my calibration file would contain the calibration file of my audio interface AND the acoustic calibration of my room.


What do you think? Is it realistic to proceed like this in order to minimize the reflection of my room? Is there a functionality in REW which i missed?

Looking for your feedback!

thanks!
Victor from Berlin.
 

John Mulcahy

REW Author
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Apr 3, 2017
Messages
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Is it realistic to proceed like this in order to minimize the reflection of my room?
No, that won't work. You cannot calibrate away a reflection and the effects of the floor reflection will vary depending on the physical dimensions and drive unit locations of what you are measuring and your measuring distance.
 

asb

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May 5, 2024
Messages
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Hello mister Mulcahy,

First of all, thank you very much for your very quick reply last Sunday.
I wanted to find a solution before replying here so it's why i am replying a few days later.

After seeing your message, I tried to proceed to ground plane measurements and it solved my problematic. Now i am ready to have more experience with testing and REW!
and Thanks for developing REW. It's good and stimulating to see engineer like you developing open source tool.

Also:
As i have the chance to discuss here with you, feel free to share the name of a book related to acoustic testing :) :)

have a good week end!
Victor from Berlin
 
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