This article is part of a series; see Speech Reinforcement.
Being able to take measurements is very important, as it removes much of the guesswork involved in making a sound system effective.
You should be able to do at least the following measurements:
sound pressure level (SPL)
realtime analyzer (RTA)
Audio analyzers are available that can provide much of this functionality. However, the following hardware acts as additional audio inputs/outputs for a computer (via USB) and can be used not only for room measurement, but also for signal processing in general. These been selected for some combination of portability (size), versatility, and quality.
You will also need a measurement microphone. Dayton Audio sells three different test measurement microphones, and provides a unique calibration file for each microphone (cross-referenced by serial number)—this can be used to set a calibration curve for compensation. I recommend the EMM-6. I have also used the dbx RTA-M microphone.
REW (Room EQ Wizard) is Java-based, and available for Windows, Mac OS X, and Linux. It provides many measurement functions. If you plan to use it, please consider reading all of the REW documentation. See also Room EQ Wizard SPL Calibration – Without an SLM.
BRP-PACU is free and open source software for Mac OS X and Linux. It provides a pink noise generator and an analyzer and calculates transfer functions. It uses JACK for audio connections. See also the latest (as of 2015) blog entry regarding BRP-PACU.
Jaaa, Japa, and Jnoise are all tools for Linux that connect to the JACK sound server (or standard ALSA) and provide signal/noise generation and spectrum analyzers.
If you plan to do much signal processing on your computer, you may want to run the JACK audio connection kit on Linux. JACK provides audio routing between sound hardware and applications that support JACK. There are many applications that support JACK, and LV2, LADSPA, and DSSI plugins can be connected too.
Android apps from Keuwlsoft; especially SPL Meter and Spectrum Analyzer. Measurement quality with a stock phone/tablet microphone may be quite poor. For possibly better results, these could be used with a Dayton Audio iMM-6.