Psychoacoustic data for the study "Notched noise reveals differential improvement in the neural representation of sound"

Psychoacoustic data for Matlab including audiometric thresholds from the study "Notched noise reveals differential improvement in the neural representation of sound" The study was approved by the Ethics committee of the University of Oldenburg. Stimuli were sinusoidally amplitude-modulated (SAM) tones with a fixed modulation frequency fm = 128 Hz at full modulation depth of 100% and fc = 4000 Hz. The procedure was a two-interval, two-alternative forced-choice task (2I-2AFC). The task of the subject was to indicate whether the SAM tone in the second interval was perceived to the left or the right of that presented in the first interval. The stimuli had synchronous onset and offset gating in both ears, so that the SAM tones differed only in their ongoing interaural phase difference of the envelope (IPDENV). SAM tones had a carrier frequency fc of 4 kHz and were presented to the subject via Sennheiser HD-650 headphones at a SPL of 65 dB. Levels where calibrated using a sound-level meter and an Artificial Ear Type 4153 (Brüel & Kjær). Digital-analog conversion was carried out by ADI-s DAC FS (RME) with 32 bit and a 48-kHz sampling rate. Stimuli were generated digitally using the AFC-software package. The subjects were seated in a double-walled, sound-attenuating booth and responded by pressing a key on a standard computer keyboard. Visual feedback was provided after each trial. The 300-ms SAM tone duration included 20-ms cos2 rise-decay ramps. A 50-ms silent interval separated the two intervals. A next pair of intervals was presented 500 ms after the subject responded. The IPDENV of the stimuli presented in the two intervals were symmetrical around zero, so that in one of the two intervals, the right ear was leading, in the other the left ear led by the same IPDENV. Subjects could thus make their decision based on a ΔIPDENV (= 2 IPDENV used in the individual intervals) difference between the two intervals. The experiment consisted of two phases. In the first phase (Figure 1), the threshold IPD-value was estimated for the baseline condition (with spectrally-flanking notched noise presented to both ears with no interaural correlation). An adaptive ‘four-down, one-up’ staircase procedure controlled the ΔIPDENV, meaning that the ΔIPDENV was decreased after four correct responses in a row and increased after each incorrect response, adapting towards a proportion correct of 0.84. This target rate of 0.84 provides a large result space for a deterioration before a floor is hit at chance level 0.5. Each adaptive track started at a ΔIPDENV of 0.4p radians. The maximum allowed ΔIPDENV value was 0.8p, because a decline of sensitivity is expected for higher values. With this upper limit for the adaptive tracking variable, a slightly lower upper bound of approximately 0.7p radians, is expected for the mean values. The initial step size was a factor of 2, which was reduced to 1.414 (21/2) and 1.189 (21/4) after the first and second ‘down-up-reversal’. An adaptive track was terminated after 10 reversals at the minimum step size. This sequence was repeated three times for each subject. In the second part (Figure 2), the proportion correct for a fixed ΔIPDENV was measured in four different conditions: (1) in quiet, (2, 3) in spectrally-flanking notched noise at only the left or right headphone channel, and (4) in a control condition with the same interaurally uncorrelated notched noise as in the first part. For the second, third, and fourth conditions, the spectrally-flanking noise was presented continuously, to minimize binaural interference. The ΔIPDENV was the geometric mean of the thresholds from the first part. The spectrally-flanking notched noise had a spectral level of -35 dB relative to the SAM tone. The notch was centered at 4 kHz and had a width of 800 Hz between 3600 and 4400 Hz (w = 20%). To avoid the use of low-frequency distortion products arising from nonlinear peripheral auditory processing, a continuous diotic noise, low passed at 1.3 kHz with a relative spectral level of g = -35 dB.Hz-1 was added in all conditions.本数据集为适用于Matlab的心理声学数据，包含来自研究《凹口噪声揭示声音神经表征的差异性改善》（Notched noise reveals differential improvement in the neural representation of sound）的听阈数据。本研究已通过奥尔登堡大学伦理委员会批准。 实验刺激为正弦调幅（sinusoidally amplitude-modulated, SAM）纯音，调制频率fm固定为128 Hz，调制深度达100%，载波频率fc为4000 Hz。 实验范式为二区间二选项迫选任务（two-interval, two-alternative forced-choice, 2I-2AFC）。被试需判断第二区间呈现的SAM纯音相较于第一区间，是感知为偏左还是偏右。两类刺激的双耳触发与偏移门控同步，仅在包络耳间相位差（interaural phase difference of the envelope, IPDENV）上存在差异。SAM纯音载波频率fc为4 kHz，通过森海塞尔HD-650（Sennheiser HD-650）耳机以65 dB声压级（sound pressure level, SPL）呈现。声级通过声级计与人工耳Type 4153（Brüel & Kjær）进行校准。数模转换由ADI-s DAC FS（RME）完成，采样位数为32位，采样率为48 kHz。刺激通过AFC软件包数字化生成。被试坐在双层隔音隔声室中，通过标准计算机键盘按键作答，每轮试次后会提供视觉反馈。SAM纯音时长为300 ms，包含20 ms的cos²型升降斜坡。两区间之间设有50 ms的静默间隔，被试作答后500 ms会呈现下一组区间。两个区间的IPDENV以0为中心对称分布，其中一个区间右耳相位领先，另一区间左耳以相同IPDENV领先。因此被试可基于两区间的ΔIPDENV（即单个区间IPDENV的2倍）差异进行判断。 实验分为两个阶段。第一阶段（图1）：针对基线条件（双耳均呈现频谱旁带凹口噪声且双耳互相关为0）估算阈值IPD值。采用自适应“四降一升”阶梯式程序控制ΔIPDENV：连续4次正确作答后ΔIPDENV减小，单次错误作答后ΔIPDENV增大，适配至正确率0.84的目标水平。该0.84的目标正确率可在达到随机水平0.5的地板效应前，为表现劣化留出充足的结果空间。每条自适应轨迹初始ΔIPDENV为0.4π弧度，最大允许ΔIPDENV为0.8π弧度，因更高数值下敏感性会出现下降。以此为自适应追踪变量的上限，预期平均阈值略低于该上限，约为0.7π弧度。初始步长为2倍系数，在首次和第二次“降升反转”后分别将步长调整为1.414（即√2）与1.189（即2^(1/4)）。当达到最小步长且完成10次反转后，终止当前自适应轨迹。每名被试需重复该流程3次。 第二部分（图2）：针对固定ΔIPDENV测量4种不同条件下的正确率：(1) 安静环境；(2, 3) 仅左或右耳机声道呈现频谱旁带凹口噪声；(4) 与第一阶段相同的双耳非相关凹口噪声的对照条件。 对于第2、3、4种条件，频谱旁带噪声会持续呈现，以最大限度降低双耳干扰。ΔIPDENV采用第一阶段测得阈值的几何平均值。频谱旁带凹口噪声的频谱级相较于SAM纯音为-35 dB。凹口中心位于4 kHz，带宽为800 Hz（覆盖3600 Hz至4400 Hz，w=20%）。为避免外周听觉非线性处理产生的低频失真产物，所有条件下均添加了截止频率1.3 kHz的双耳同相（diotic）连续噪声，其相对频谱级为g = -35 dB·Hz⁻¹。