Pa 5 programmable attenuators

Seven frequencies were used as ipsilateral primary tones, delivered to the right ear, for eliciting DPOAEs at different positions of the cochlea (f2 = 1,440, 2040, 2,884, 4,080, 5,769, 6,125 and 8,160 Hz), while contralateral broad-band noise (~ 60 dB SPL) was delivered to the left ear. Both stimuli were digitally generated by two synchronized PCI boards (6,071-E, National Instruments) at 100,000 samples/s, attenuated with PA-5 programmable attenuators (System 3, Tucker-Davis Technologies) and delivered through ER-2 transducers (Etymotic Research) sealed to both external auditory meatus and pinna. Primary tones were presented at a rate of 4 Hz with a duration of 15 ms, 5 ms rise/fall time, a fixed ratio of f2/f1 = 1.25 and L1/L2 = 65/60 dB SPL, with a delay of 200 ms. Contralateral non-continuous broad-band noise (BBN, 0.2–10 kHz) was delivered at a presentation rate of 4 Hz with a duration of 170 ms. At the beginning of each experiment sound pressure level calibrations were made in both ears using an Etymotic^® microphone.

Ipsilateral tones (right ear, 15 kHz at 80 dB SPL) and contralateral broadband noise (CBN) (left ear, 55–60 dB SPL) were digitally generated by two synchronized multifunction computer boards at 100,000 samples/s (PCI-6071-E, National Instruments^®, TX, USA), attenuated by PA-5 programmable attenuators (system III, Tucker Davis Technologies^®, FL, USA). We decided to use 15 kHz tones due to evidence of a higher density of olivocochlear innervation at this position of the cochlea in mice [24 (link)]. Auditory stimuli were delivered via two tweeters (one for ipsilateral and the second for contralateral auditory stimuli) (Realistic super tweeter, frequency response 5–40 kHz, Radioshack^®, TX, USA) through tubes sealed to the external auditory meatus. Ipsilateral tones were presented with alternating polarity at 4 Hz rate, 5 ms duration, and 0.5 ms rise/fall time and were used to obtain ipsilateral auditory brainstem responses and contralateral ACEP. Contralateral non-continuous broadband noise (5–40 kHz) was presented at 4 Hz with a duration of 170–200 ms.