Laptop-based hearing testing system. Custom software on the laptop runs a calibrated sound card (ECHO Indigo IO, Echo Audio, Santa Barbara, CA), ear probe (Grason-Stadler Inc., Eden Prairie, MN) combination to perform the audiological tests. Separate devices are used for tympanometry (Madsen Otoflex 100) and ABRs (GSI AudioScreener), and the results from these devices are communicated back to the laptop via Bluetooth, and infrared respectively. The overall laptop-based hearing testing system with associated hardware includes: (a) Questionnaire administration to gather data on self-reported hearing and exposure to noise, drugs and toxins, (b) Threshold audiometry (either Békésy or Hughson-Westlake) to measure overall hearing ability, (c) Distortion product otoacoustic emission (DPOAE) testing to assess cochlear function, (d) Gap detection testing to assess central auditory processing, (e) Tympanometry to assess middle ear function, and (f) Auditory brainstem response testing to assess brainstem pathways in adults who cannot complete the gap-detection test