Running the Test Tones to measure room acoustic response
It is recommended that you will record the test tone at the same bit depth and sampling rate as the reference test tone which is 24-bit/48KHz. Finally you can hit the record button and while test tone will be played; the condenser microphone will then capture the room response by recording the monitored test tones. Be careful of very loud volume, it can damage your ear. I recommend you will go outside of your control room during this test. Also I recommend doing the test 3 times, first at 50% monitored volume, then the second at 40% volume and the last at the softer volume of 35%. The objective is to check the room response at different volumes and decide on the best monitoring volume for mixing accuracy. For example below is the Reaper output after recording the test tones to measure room response at 3 different volumes:
Analyzing the Test Results
First, normalize all the waves to -0.2dB (which is similar at the test tone maximum peak volume). Then run the result through frequency analysis software. I am using Adobe Audition 1.5 for analyzing the frequency response of the recorded test tones. If the recording software does not have this feature, you can use this open source solution.
Download Right Mark Audio Analyzer then install it to your computer. Launch the program then click the spectrum analyzer icon (see screenshot):
Then it will open the wav file for analysis automatically plots the results; select a high FFT size such as 65536. Finally below are the room acoustic analysis results of the above test:
The ideal or perfect result is the bottom graph (labeled as “ideal result). Monitoring at lower volume during mixing (around 30% of the maximum volume) results in a flatter/smoother overall frequency response. Monitoring at louder volumes can slowly inflate the bass even with bass traps because there are leaking reflections of the bass at louder monitoring volume. For some setups, 30% of the maximum volume is very quite; so slowly increase the monitor volume until all the musical instruments can now be heard. The acoustic treatment of the room above is very basic although the result above says that much can still be improved with the current acoustical treatment. If you find out that the room responses is severely skewed or out of balance, then add more acoustic treatments and do it correctly.
Content last updated on July 21, 2012