Er 4pt

The group used a CLV 2534-4 LDV with a VIB-E-220 acquisition unit and corresponding VibSoft-20 acquisition software (all Polytec GmbH, Germany) for measuring SFV. The microphone (ER-7C, Etymotic Research) was inserted into the auditory canal along with the earphone (ER-4PT, Etymotic Research) probe. The microphone probe was situated at about 1–2 mm in front of the TM. Excitation signals were single sine waves generated using a wave generator (Agilent 33210A 10 MHz) and an amplifier (B&K type 2718). LDV angle of incidence was not recorded but documented to be $\mathrm{\Theta }\le {30}^{\circ }$ .
Velocity measurements were averaged 30 times and quality-checked using SNR for each frequency, with a threshold of SNR > 10 dB below 1 kHz and SNR > 20 dB for higher frequencies^{15 (link)}. Data from this group will be denoted as “Shanghai” and method “A”.

Frequency responses were calibrated for the headphones. Acoustic stimuli were generated digitally, converted to an analog signal at ∼200 kHz sampling rate (RZ-6 Multi I/O Processor, Tucker-Davis Technologies), attenuated and conveyed to the headphones (ER4-PT, Etymotic Research). The standard search stimulus presented to the contralateral ear was a broadband stimulus (white noise bursts) with a duration of 200 ms and squared-cosine rise/fall times of 5 ms. The same stimulus with a duration of 20 ms was presented on the ipsilateral ear after the first 100 ms. The inter-stimulus interval for each repetition was 900 ms. For all recordings, stimulus presentation was pseudo-randomized. Acoustically evoked responses were searched for by administering binaurally delivered noise stimuli without interaural time and intensity differences. A neuron’s best frequency (BF) and threshold were determined by means of binaurally identical (interaural intensity difference/interaural time difference = 0) sinus tone stimulation. BF was defined as the frequency that elicited responses at the lowest sound intensity. Threshold was assigned to the lowest sound intensity evoking a noticeable response at BF. All stimuli applied in the course of our experiments were based upon these characteristics.