Development of a fast method for determining psychophysical tuning curves

Abstract

Psychophysical tuning curves (PTCs) can be used to assess the frequency selectivity of the auditory system and to detect and delimit "dead regions" in the cochlea. However, the traditional method for determining PTCs takes too long for use in clinical practice. We evaluated a fast method for determining PTCs, using a band of noise that sweeps in centre frequency and a Békésy method to adjust the masker level required for threshold. The shapes of the PTCs were similar for the fast and traditional methods, for both normally hearing and hearing-impaired subjects. Rates of change of masker level of 2 dB/s or less gave the most reliable results. A relatively wide bandwidth (20 percent of the signal frequency or 320 Hz, whichever is the smaller) was needed to minimise the influence of beat detection. When the signal frequency fell within a dead region, the fast method gave PTCs with shifted tips.

Stimulus-Frequency Otoacoustic Emission Suppression Tuning in Humans: Comparison to Behavioral Tuning

“…As a result, the synthesized masker waveform was a narrowband noise with a center frequency that changed uniformly in time on a log frequency scale over the 0.5f probe -2f probe range. To minimize beat-detection cues, the masker bandwidth was set to 200 Hz for probe frequencies~1,000 Hz and to 320 Hz for probe frequencies~4,000 Hz (Kluk and Moore 2004;Sęk et al 2005). The masker level never exceeded 90 dB SPL.…”

“…The probe was 500 ms in duration tone with 25 ms rise/fall times, presented with interstimulus intervals of 200 ms. The masker waveform was synthesized using MATLAB and stored on the hard drive (for details regarding signal synthesis see Sęk et al 2005;Sęk et al 2007;Sęk and Moore 2011). In brief, the 240-s masker waveform was synthesized by overlapping 7,500 short duration (~46 ms) segments of narrowband noise.…”

“…The PTCs were collected with a "fast" method (Sęk et al 2005;Charaziak et al 2012). The gated tonal probe, fixed in frequency, was presented simultaneously with a narrowband masker (200 or 320 Hz wide) for which the level was controlled by the subject via a button, as in Békésy audiometry, while the masker center frequency changed continuously in time from low to high (upward sweep) or from high to low (downward sweep).…”

The development of a fast method for recording Schroeder-phase masking functions

“…To account for a known 'hysteresis effect' in Békésy tracking where measured curves can be shifted by small delays in participant responses (Sęk, Moore, Kluk, Wicher, 2005;Sęk & Moore, 2011), two sweep directions were applied: forward (from C = -1.1 to C = +1.1) and backward (from C = +1.1 to C = -1.1), with the final curve being the average of the forward and backward sweeps. …”

“…Our version of the Schroederphase masking procedure was inspired by the use of the Békésy tracking technique to record psychophysical tuning curves (PTCs) (Zwicker, 1974;Sęk et al, 2005). To record PTCs using this technique, the frequency of the masker is constantly swept and a repetitive probe of fixed frequency is presented at the same time.…”