Data low-frequency hearing thresholds (LFSH).

A small percentage of the general population reports almost constant humming or pulsing low-frequency sound percepts (LFSPs), while others in their vicinity, such as family members, often do not perceive these sounds. The origin of these LFSPs remains to be elucidated and may, or may not, be related to external sound sources. The underlying causes of these perceptions could also be subjective and belong to the tinnitus family, especially in cases where no external sound source sufficiently explaining the LFSP can be found. The present study puts forth two hypotheses to explain the phenomenon, based on both subjective and objective auditory phenomena: an unusually high auditory sensitivity to low-frequency sound, and hearing one’s own low-frequency spontaneous otoacoustic emissions (SOAEs), sounds actively produced by the inner ear as a normal, physiological by-product of cochlear amplification. The present study employed high-resolution, low-frequency hearing threshold measurements and SOAE measurements in 28 individuals with LFSPs and in control groups devoid of LFSPs. LFSP complainants self-reported hearing an LFSP at a median frequency of 50 Hz, obtained with a frequency-matching procedure. With a few clear exceptions, complainants most often did not present unusually sensitive low-frequency hearing thresholds. Furthermore, hearing threshold microstructure was comparable to that of the control group. In addition, no SOAEs in the low-frequency range could be measured. Based on our results, while cases of hearing physical external sound sources are not ruled out, we suggest that subjective tinnitus in the low-frequency range is often the reason behind hearing these LFSPs.普通人群中约有小部分个体自述几乎持续感受到嗡嗡样或搏动性低频听觉感知（low-frequency sound percepts，LFSPs），而其身边的亲友等旁人通常无法感知此类声响。此类LFSPs的成因尚未阐明，其可能与外界声源相关，也可能无关。该类听觉感知的潜在诱因也可能为主观性因素，归属于耳鸣（tinnitus）范畴，尤其是当无法找到可充分解释LFSPs的外界声源时。本研究基于主、客观听觉现象，提出两种可解释该现象的假说：一是对低频声音存在异常高的听觉敏感性，二是可感知自身的低频自发性耳声发射（spontaneous otoacoustic emissions，SOAEs）——此类声音由内耳主动产生，是耳蜗放大功能的正常生理性副产物。本研究针对28名存在LFSPs的个体以及无LFSPs的对照组群体，开展了高分辨率低频听阈测量与SOAE测量。通过频率匹配程序，存在LFSPs的受试者自述感知到的LFSPs中位频率为50 Hz。除少数明确的例外情况外，此类受试者的低频听阈大多未表现出异常敏感的特征。此外，其听阈微结构与对照组群体无显著差异。同时，未在低频范围内检测到SOAEs。基于本研究结果，尽管未排除可感知真实外界声源的情况，但我们认为低频主观性耳鸣通常是此类个体感知到LFSPs的核心诱因。