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Four approaches to room acoustic measurement

This article covers the four main ways in which you can measure your room’s acoustics. In decreasing ease of use order these are:

  • Integrated software / hardware packages such as XTZ Room Analyzer and Dayton Audio Omnimic
  • Standalone software packages and your choice of measurement microphone, cabling and soundcard such as Room EQ Wizard
  • Hardware devices such as NTIs XL2
  • SPL meter, graph paper and test tones (please don’t use this method!)

 

Integrated software and hardware acoustic measurement packages

A recent development are integrated software and hardware acoustical measurement packages such as XTZ Room Analyzer and Dayton Audio Omnimic where you literally get everything you need to measure your room in one box. The software side of these packages is designed to be easy to use, since they will be typically used by beginners and those with no experience of room measurement. The last thing you want to waste time on is figuring out how to use the software to take measurements! Rather spend that time experimenting with speaker and listener positioning, acoustical treatment and room correction.

XTZ Room Analyzer

Pros:

  • Relatively low cost
  • Designed from the outset to be easy to use
  • One integrated hardware and software package which has everything you need to measure your room in one box
  • Doesn’t require you to figure out which soundcard, cables and what calibrated measurement microphone you need

Cons:

  • May not have all of the in-depth analysis capabilities of standalone measurement software / hardware combinations

 

Standalone software plus separately purchased measurement measurement, soundcard and cabling

There are hundreds of standalone measurement packages on the market, from the free and excellent (Room EQ Wizard) to very expensive (EASERA). Most acoustical measurement software is generic, in that it is not designed expressly for the purpose of taking measurements of a room’s acoustics. As such they are often over-engineered for our purpose and consequently difficult to use.

Pros:

  • Often very functionally rich, containing advanced analysis functionality such as phase, harmonic distortion and group delay analysis. This can be useful if you trying to design speakers as well as fixing the acoustical distortions introduced by your room.

Cons:

  • Generally not beginner friendly and often complicated to use because of the number of non-room measurement related functions they include
  • Accurate sound pressure level readings require that you calibrate the system using a separate microphone calibrator or sound pressure level (SPL) meter
  • Require that you identify and purchase a suitable soundcard, calibrated measurement microphone, cabling and stand. It can take a lot of research and time to get these things and most of the time you will have to order from multiple suppliers.

 

Hardware measurement device

Back in the good old days you could only buy hardware based acoustical measurement equipment. Nowadays the only people who tend to use these tools are those who work in nightclubs, professional sound or car audio. Sometimes you will find people who use a software based system most of the time but carry a hardware device to carry out quick spot checks or for use as a backup in case the battery dies at an inopportune time. A couple of good ones are the NTI XL2 and Phonic PAA3.

Phonic PAA3

Pros:

  • Some models are portable
  • Generally robust, often designed for arduous environments
  • Quick start up, since they don’t require you to boot up your PC

Cons:

  • Often expensive
  • Often provide no energy / time or time / energy / frequency measurements. Identifying problematic reflections and room modes is therefore made much more difficult, if not impossible.

 

 

Sound pressure level (SPL) meter, a test tone CD and graph paper or a spreadsheet

This method uses a CD containing test tones played at different frequencies such as 60Hz, 65Hz, 70Hz, etc and a SPL meter. You then play each tone and record the number shown on your SPL meter on a spreadsheet or on a sheet of graph paper. In this way you can plot the frequency response of your room.

Pros:

  •  Cheap

Cons:

  • Very time consuming even to put together a single frequency response. Given that optimizing your system is an iterative process involving testing multiple locations of speaker and listener positions this quickly turns into an long and drawn out exercise.
  • Cannot understand the energy / time or time / energy / frequency behavior of your room. Identifying strong early reflections and room modes is therefore made much more difficult, if not impossible.

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