The most important tools I use are my ears. Regardless of specifications and numbers, at the end it should simply sound perfect. Simply listening can explain why something sounds or doesn't sound good.
The acoustics in a room is for a major part determined by the geometry. In order to understand the behaviour of a room one should investigate the geometry of a room. This I do using Rhinoceros and Grasshopper with special by Kahle Acoustics developed plug-ins, my primary design tool. The geometry can be investigated statical, e.g. an existing design, or dynamical using Grasshopper to design and test by ray-tracing real time. In this way a design can be made very efficiently and parts of a room can be tailored with high precision and acoustic efficiency.
Although not always necessary, a design can be verified using acoustic simulation software. Designs made in Rhinoceros can efficiently be exported to CATT after which an acoustics computer simulation can be made.
In order to determine objective acoustical parameters I use DIRAC room acoustic measurement software developed by Acoustics Engineering.
To excite a room one needs a source. For this I use two home made sources. The tube I use to perform a so called “decrease-with-distance” measurement that enables to create an acoustical fingerprint of a room. This measurement makes it easily possible to compare the results with e.g. Barron's revised theory. The box, compact and handy to transport, I primarily use for reverberation time measurements.