The characteristics of human otoacoustic emissions (OAEs) have not been thoroughly examined above the standard audiometric frequency range (>8 kHz). This is despite the fact that deterioration of cochlear function often starts at the basal, high-frequency end of the cochlea before progressing apically. Here, stimulus-frequency OAEs (SFOAEs) were obtained from 0.5 to 20 kHz in 23 young, audiometrically normal female adults and three individuals with abnormal audiograms, using a low-to-moderate probe level of 36 dB forward pressure level (FPL). In audiometrically normal ears, SFOAEs were measurable at frequencies approaching the start of the steeply sloping high-frequency portion of the audiogram (∼12–15 kHz), though their amplitudes often declined substantially above ∼7 kHz, rarely exceeding 0 dB SPL above 8 kHz. This amplitude decline was typically abrupt and occurred at a frequency that was variable across subjects and not strongly related to the audiogram. In contrast, certain ears with elevated mid-frequency thresholds but regions of normal high-frequency sensitivity could possess surprisingly large SFOAEs (>10 dB SPL) above 7 kHz. When also measured, distortion-product OAEs (DPOAEs) usually remained stronger at higher stimulus frequencies and mirrored the audiogram more closely than SFOAEs. However, the high-frequency extent of SFOAE and DPOAE responses was similar when compared as a function of the response frequency, suggesting that middle ear transmission may be a common limiting factor at high frequencies. Nevertheless, cochlear factors are more likely responsible for complexities observed in high-frequency SFOAE spectra, such as abrupt amplitude changes and narrowly defined response peaks above 10 kHz, as well as the large responses in abnormal ears. These factors may include altered cochlear reflectivity due to subtle damage or the reduced spatial extent of the SFOAE generation region at the cochlear base. The use of higher probe levels is necessary to further evaluate the characteristics and potential utility of high-frequency SFOAE measurements.
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机译：在标准测听频率范围（> 8 kHz）之上，还没有对人体耳声发射（OAE）的特性进行彻底检查。尽管存在这样的事实，即耳蜗功能的恶化通常始于耳蜗的基础高频末端，然后才逐渐发展。在这里，使用36dB前向压力水平（FPL）的低至中度探头水平，在23位听力正常的年轻女性成年人和3位听力图异常的个体中，从0.5到20 kHz获得了刺激频率的OAE（SFOAE）。在听力正常的耳朵中，可以测量SFOAEs的频率接近听力图陡峭倾斜的高频部分的起始频率（〜12-15 kHz），尽管它们的幅度通常会下降到大约7 kHz以上，很少超过8以上的0 dB SPL千赫。这种幅度下降通常是突然的，并且发生的频率在对象之间是可变的，并且与听力图没有太大关系。相比之下，某些耳朵的中频阈值较高，但正常的高频灵敏度区域可能在7 kHz以上具有令人惊讶的大SFOAE（> 10 dB SPL）。当还进行测量时，失真产物OAE（DPOAE）通常在较高的刺激频率下仍保持较强的强度，并且与SFOAE相比，更能反映听力图。但是，当将SFOAE和DPOAE响应的高频程度作为响应频率的函数进行比较时，表明中耳传播可能是高频的常见限制因素。尽管如此，耳蜗因素更可能是导致高频SFOAE频谱中观察到的复杂性的原因，例如突然的幅度变化和在10kHz以上的狭窄定义的响应峰以及异常耳朵中的大响应。这些因素可能包括由于细微的损伤或耳蜗底部的SFOAE生成区域的空间范围减小而导致的耳蜗反射率改变。必须使用更高的探针水平才能进一步评估高频SFOAE测量的特性和潜在的实用性。
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