AES Section Meeting Reports

Melbourne - August 8, 2022

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Following the AGM Chairman Graeme Huon introduced John Mulcahy, the developer of the Room EQ Wizard (REW) software package.

John started his talk by describing his free acoustic and audio measurement software REW, indicating that it was first released in 2004, supports off-the-shelf audio interfaces, is available for Windows, MacOS and Linux, targets a wide range of users from novice to expert, and now has a 'Pro' version enabling simultaneous measurement of multiple units.

After listing the measurement features, John displayed screenshots of the setup dialogues for the various measurements, describing the settings and user-defined data, describing the measurement outputs available.

He went on to describe the tools available within the REW package: SPL meter, Signal Generator, Oscilloscope, Level meter, Inter-channel gain/phase meter, and Frequency meter.
The next feature discussed was the built-in Room Simulator function which permits the modelling of loudspeaker performance in a simple cubic space of variable dimensions with different loudspeaker placements within the 3D space.
He then discussed the wide range of analysis features available displaying a range of the results screens, then showed REW's alignment tool for measuring phase alignment between devices such as a main loudspeaker and its subwoofer, as well as a utility for deriving Thiele-Small parameters from the raw data, and then showed the graph of an impedance model indicating the model fit.

He then covered measuring RT60 in the frequency domain and displayed a waterfall plot to demonstrate the ability to show RT60 across multiple frequency bands without having to deal with filter delay effects in time domain measurements.

John then discussed the REW target user base, which covers a wide range from audio hobbyists to professionals, as well as equipment manufacturers, car makers, educators, and even NASA.
He indicated that there were approximately 25,000 downloads of REW per month.
He described how REW has evolved from a single-purpose acoustic optimization tool to the current version, adding many measurement functions along the way.

He indicated that he chose Java as the development platform because with Java he was able to offer REW on multiple platforms (Windows, Mac, Linux), without having to modify the code for each.
He then discussed the challenges of development, and how Java's downside was that at the time there were not many existing Java libraries for functions such as graphical interfaces, mathematical and scientific functions, and audio parameter extraction. This resulted in his having to write much code from scratch using algorithms ported from other languages.

John went on to discuss the difficulty of finding appropriate audio standards to use in the design of his software, citing the absence of standards for data presentation (eg: smoothing), the broadness of some measurement standards, and the lack of reference data to demonstrate adherence.

Following his presentation, John answered a wide range of questions on subjects ranging from specific use cases, choice of measurement microphones and speakers, speech clarity measurement, and the use of REW with miniDSP products.

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AES - Audio Engineering Society