Subject: Summary: Affordable/simple audio hardware for psychoacoustic experiments From: Daniel Oberfeld <oberfeld@xxxxxxxx> Date: Thu, 19 Jul 2007 16:22:10 +0200 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>Dear list, some weeks ago, I asked if someone could recommend hardware for running psychoacoustic experiments like the measurement of absolute and discrimination thresholds in undergraduate labs in Experimental Psychology. Now here’s a summary of the replies I received from the list. Thanks a lot to all who replied! To first give you some more details concerning my question, my idea was to use a low-noise audio interface with output power sufficient to drive headphones, so that low-impendance phones like the Sennheiser HDA200 we use because of its good sound insulation can be connected directly to the audio interface. Especially for an undergraduate lab, this solution would have the advantage of having as few knobs as possible, and thus to avoid the students being tempted to change the settings... Alternatively, a low-noise headphone amplifier could be combined with an audio interface, at the expense of additional cabling and knobs/switches that can loose their correct settings. Volker Hohmann recommended the Edirol UA-25 two-channel bus-powered USB audio interface. It includes a headphone output with an analog level control. According to the manufacturers specs, the noise is -96 dBu (A-weighted, presumably at the line and not the headphones output), and the dynamic range is 105 dB. Additionally, Volker mentioned the sound-insulated headphones VIC Firth SIH 1 (http://www.thomann.de/de/vic_firth_sih1_gehoerschutz.htm) and the headphone amplifier Behringer HA 4400 (now Behringer sells the HA 4700, see http://www.thomann.de/de/behringer_ha4700_powerplay_proxl_kopfhoererverstaerker.htm; noise < 90 dBu, dynamic range 110 dB(A) according to Behringer). Leon van Noorden also uses a Behringer HA 4600 amp and reports good sound quality. Dan Freed had an interesting suggestion: He uses a combination of USB soundcard and heaphone amp (HeadRoom BitHead, http://www.headphone.com/products/headphone-amps/the-mobile-line/headroom-total-bithead.php) and said that the system sounds pretty clean even in bus-powered mode. No specs are available. Piotr Majdak recommended the cheap (45 Euros) Millenium HP1 amp (http://www.thomann.de/at/millenium_hp1_headphone_amp.htm; no specs available). He uses it in a sound-insulated room and it produces no audible noise in HDA200 phones. He solved the problem with the analog volume knob simply by fixating it with some glue. Finally, Ralph Muehleisen suggested to check out the four-channel Audiotrak Maya44 (http://www.esi-pro.com/viewProduct.php?pid=62), which according to the manufacturer features a high-fidelity headphone amplifier and has a dynamic range of 108 dB. I did some own research on the internet, concentrating on external (USB or Firewire) audio interfaces with more than two channels (because I often present visual signals synchronized with audio simply by connecting low-power LEDs to the additional outputs). The best (but unfortunately not really affordable) solution seems to be the RME Fireface 400 (8 channels I/O, ADAT, etc.). It has the unique advantage of featuring two outputs designed for driving headphones but at the same time providing the same dynamic range as the other outputs. Additionally, the output level can be software-configured for 3, 13, or 19 dBu, thus providing additional dynamic range, and there are no analog volume controls, so that the unit seems “student proof”. Measurements by Anselm Goertz published in the german Sound & Recording magazine showed a noise level of −93 dBu (unweighted) at maximum output gain and a dynamic range of 112 dB (unweighted). So RME once again offers a very useful device for psychoacoustics (quite a few people on this list use the excellent RME ADI 8-Pro AD/DA converter). The following devices also seem potentially suitable for psychoacoustics: * ECHO AUDIOFIRE 4 (4-channel firewire interface). It features 4 balanced analog outputs, with the nominal output level software configurable to +4dBu or -10dBV (no analog controls!), and additionally a stereo headphone output with (analog) volume control. 114dB (A-weighted) dynamic range according to the manufacturer. * Lake People G93 headphone amp (http://www.lake-people.com). Manufacturer says Dynamic range: > 125 dB (A-wtd), Noise: < -98 dBu (A-wtd), THD+N: < 0.002% (800mW / 100R). It can be adapted to different headphone impendances and efficiency factors. To summarize, some of the devices mentioned above could even represent an alternative to specialized setups like the TDT system. It would fantastic if an evaluation of these systems with a suitable audio analyzer (plus maybe psychoacoustic data) became available. So if someone here is interested and has access to audio measurement facilities, just send me an email. Daniel -- Dr. Daniel Oberfeld-Twistel Johannes Gutenberg - Universitaet Mainz Department of Psychology Experimental Psychology Staudingerweg 9 55128 Mainz Germany Phone ++49 (0) 6131 39 22423 Fax ++49 (0) 6131 39 22480 http://www.staff.uni-mainz.de/oberfeld/