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2. Devices for recording and impulse response measurements

Dear Angelique,
the software I've been using more for impulse response measurement (if you don't want to use command lines ones, like Matlab), is Adobe Audition with Aurora plugins (from Prof. Farina, Università di Parma, Italy). Audition is an audio editing software which works really well, is stable, and supports various kinds of plugins (for real time processing and, in your case, for real time analysis like fft and rms), and the Aurora plugins offers all the support for IR extraction using MLS, sweeps (if you need to extract an impulse response from an "analogue" system, I'd definetly suggest to use the sweep technique instead of the MLS or other techniques...if you like I wrote a paper about this and I'd be more than happy to send it to you) and other signals. 
So, using just one software, you can generate MLS or sweeps (various orders and lenghts, ecc...), you can do the measurement and you can then calculate the impuse response, doing all the analysis you need (fft, room acoustics parameters, rms, ecc...).
You can find adobe audition in every audio pro shop, while for the Aurora plugins you'd better contact directly Prof. Angelo Farina (pcfarina.eng.unipr.it/).
Then, about the other parts of the system, you could install the software on a laptop PC, then buy an audio interface like the RME Fireface 400 (if you have on your laptop a 6 pin firewire connector, then the audio interface doesn't even need to be powered externally, because it'll be powered from the firewire bus...really portable!), which has multiple inputs (with 2 mic input for the kemar) and multiple outputs. 
Then I've not properly understood if you need even a microphone and a loudspeaker: in the case you need them, I'd suggest for the microphone a DPA 4060, a condenser lavalier microphone, really good quality (there is even the 4061 which can support even higher SPL level, in the case of the shot of a gun). This if you need a small microphone, while if you want a bigger one (with a bigger capsule, so a better response on low frequencies) I'd definetely suggest some B&K ones, or even a Soundfield one (the Soundfield microphones have 4 mic capsules, and they can produce various kind of signals, from mono, stereo to B-Format ones for the extraction of 3D Impulse Responses).
For the loudspeaker...it depends on the frequency response you are looking for... I'm quite sure there are no loudspeakers on the market (the audio pro one) which can reach 1 Hz, and anyway to go below 40Hz you need a loudspeaker with a woofer of at least 8"... I'd have a look on Genelec ones, or Tannoy (the Tannoy Dual Concentric ones have the tweeter mounted in the middle of the wooker, so the phase problems due to the displacement of the two drivers are eliminated...), but anyway to an amplified loudspeaker (the amplified ones are much more portable than the passive ones with external amplifiers, and they usually have dual amplification, one for high and one for low frequencies). 
Anyway, I'm not really aware about microphones, audio interfaces and loudspeakers which have a frequency response down to 1 Hz...sorry...
If you need more specific information, just write me back!
Best Regards!
Lorenzo Picinali

Lorenzo Picinali
PhD Student
Music, Technology and Innovation Research Centre
0116 2551551, internal 6770
Clephan Building CL0.19
De Montfort University