Reference hearing threshold levels for chirp signals delivered by an ER-3A insert earphone

Abstract

Objective: To establish reference hearing threshold levels for chirps and frequency-specific chirps. Design: Hearing thresholds were determined monaurally for broad-band chirps and octave-band chirps using the Etymotic Research, ER-3A insert earphone. The chirps were presented using two repetition rates, 20 and 90 stimuli/s, and with alternating polarity in blocks of one second duration. The test procedure and test conditions were in accordance with the recommendations given in . The ascending method () was applied using a step size of 5 dB. The chirps were played back from a Tucker Davies Technologies System II, and a Matlab program controlled the test setup. The results are specified in dB peak-to-peak equivalent threshold sound pressure levels (dB peETSPL). Study sample: The test group consisted of 25 otologically-normal young adults (age 18–25 years). Results: The results are in good agreement with the results from another investigation of hearing thresholds using the same chirp stimuli, and the values for the octave-band chirps are in line with the standardized reference values for corresponding tone bursts (). Conclusions: The results of the present investigation are relevant for the international standard on short duration signals, .     

婴幼儿chirp声ABR和短声ABR对比研究

目的：比较chirp声与短声ABR的V波振幅和潜伏期值,从而探讨chirp声在ABR测试时是否更具优势。方法分别用chirp声与短声两种测试声记录16例听力正常婴幼儿（24耳）的ABR,比较10～70 dB nHL不同刺激强度下两种测试声引出V波的振幅大小以及高强度和阈值强度下引出V波的潜伏期差异。结果在强度为20～70 dB nHL时,两种刺激声的V波振幅无显著差异（P>0.05）;刺激声强度为10 dB nHL时,chirp声V波的引出率较短声显著增高（分别为15/24和7/24, P<0.01）。较高刺激强度时,两种测试声引出的V波潜伏期无明显差异（P>0.05）;阈值水平时,chirp声ABR的V波潜伏期比短声ABR的V波潜伏期长（P<0.05）。结论本组听力正常婴幼儿ABR测试中chirp声相比短声增加V波振幅的优势并不显著,且I波和III波不如短声ABR典型;在临床应用chirp声之前还应进一步深入研究。     

新生儿听力筛查结果分析

目的:分析新生儿听力筛查结果情况,对临床提供参考。方法:选取我院接生的1704例新生儿,评估新生儿情况,听力筛查均采用Chirp刺激声诱发听性脑干反应(CASEABR)的方法,对初次时未通过筛查者,在1个月~42 d实施复筛,对复筛后仍未通过者进行确诊后医学干预。分析初筛通过率及复筛通过率。结果:高危患儿的初筛未通过率是32.10%(26/81),其他受试者为8.50%(138/1623)。高危患儿中有26例新生儿初筛时未通过,复筛后未通过者为3例,其他受试者在初筛时未通过者在复筛后均通过。结论:CASEABR法进行筛查具有重要临床意义,检测率高并且临床使用较为方便,可对临床诊断提供早期筛选病例,实施早期干预后可预防耳聋或是聋而不哑。     

不同程度感音神经性听力损失儿童的Chirp-ASSR测试结果分析

目的 观察不同程度感音神经性听力损失儿童Chirp声听性稳态反应(Chirp auditory steady-state responses,Chirp-ASSR)的特点,探讨Chirp-ASSR测试的临床意义.方法 对136例(272耳)5～10岁不同程度感音神经性听力损失儿童进行纯音听阈测试(pure tone audiometry,PTA)和Chirp-ASSR测试,根据500、1 000、2 000和4 000 Hz的平均听阈,将受试者分为四组,即20～dB HL组、40～dB HL组、60～dB HL组和≥80dB HL组,比较不同程度感音神经性听力损失儿童各频率纯音听阈与Chirp-ASSR反应阈的相关性.结果 ①纯音听阈≥80 dB HL组的Chirp-ASSR反应阈值比纯音听阈值高,差异有统计学意义(P＜0.05).②PTA和Chirp-ASSR的相关系数γ随着听力损失程度加重而逐渐降低,随着测试频率的增加有增大的趋势,在500 Hz和4 000 Hz之间差异有统计学意义(P＜0.05).结论 Chirp-ASSR有频率特异性,能够较好的反映听力水平,特别在轻度、中度和重度感音神经性听力损失患者中更明显.     

Ambient Pressure Evaluation Through Sub-Harmonic Response of Chirp-Sonicated Microbubbles

The sub-harmonic response generated by oscillating ultrasound contrast microbubbles has been proven to be a potentially efficient and effective measure for non-invasive blood pressure evaluation. In this work, an improved approach to ambient pressure measurement is proposed, and the general principle underlying this approach is the combination of sub-harmonic responses of microbubbles with a chirp excitation technique. Agreement between theoretical and experimental studies indicates that compared with sinusoidal excitation, the chirp technique is beneficial in that it produces bubble sub-harmonics with higher amplitudes and lower generation thresholds and thus offers better sensitivity for ambient pressure evaluations. Studies that took the chirp parameters (e.g., central frequency, bandwidth and pulse length) into account were also carried out to determine an optimized routine for the proposed method.     

Improving performance of pulse compression in a Doppler ultrasound system using amplitude modulated chirps and Wiener filtering

The use of coded excitation and pulse compression in transcranial Doppler (TCD) ultrasound systems is in the very early stages; the optimal processing scheme has yet to be determined. This study uses linear frequency-modulated (FM) chirps with 0.8-MHz bandwidth and compares the use of pulses with and without amplitude modulation and also matched filtering vs. Wiener filtering. The results demonstrate that using amplitude-modulated pulses vastly improves the axial resolution and provides a more predictable mainlobe-to-sidelobe distance in the radiofrequency (RF) signal. It is also shown that a Wiener filter can provide better performance than a matched filter, in terms of axial resolution and sidelobe level in the RF signal and signal-to-noise ratio in conventional sonograms. Although this study uses a TCD system, the techniques described are equally as applicable in other Doppler ultrasound devices.     

Evaluation of waveform,latency and amplitude values of chirp ABR in newborns

Objectives

There has been a rapid growth in using chirp stimuli for evoking auditory brainstem response (ABR). This study aims to investigate the waveform morphology, latency, and amplitude values in newborns and compare them with those evoked by the click in order to determine whether chirp-evoked responses are easier to detect at near-threshold values, as has been proposed, and to assess the usefulness of the chirp stimulus in improving ABR detection thresholds in this population.

Methods

Chirp- and click-evoked ABR were measured in 96 normal-hearing newborns (52 males and 44 females) using the MB11 BERAphone^®. Only children who passed the hearing screening and were not older than 5 days were included in this study. Two stimulation levels were used: 40 dB nHL and 60 dB nHL. The stimulation rate was 20.3 s^–1. The recorded ABR were analyzed based on visual identification of waves I, III, and V, and their amplitude and latency values.

Results

Chirp-evoked responses showed clearly larger wave amplitudes compared to those evoked by click stimulus. The gain in amplitude for wave V was 77% for 60 dB nHL and 100% for 40 dB nHL, for wave III the gain was 22% at 60 dB nHL and 46% at 40 dB nHL and for wave I the gain was 64% and 100%, respectively. Generally, the gain in amplitude associated with the chirp was greater at the lower stimulus level of 40 dB nHL. The wave's latencies were shorter in response to the chirp stimulus. Interpeak intervals differed between click-evoked and chirp-evoked ABR, slightly in the I–III interval and significantly in the I–V interval.

Conclusions

Chirp-evoked potentials are distinguished from click-evoked potentials by their significantly larger ABR amplitudes. Therefore they are expected to yield more reliable results and shorter measurement times. It should be noted that, for diagnostic purposes, the typical peak latencies of chirp-evoked ABR are clearly different to those of clicks.     

Comparison between ABR with click and narrow band chirp stimuli in children

Objective

Click and chirp-evoked auditory brainstem responses (ABR) are applied for the estimation of hearing thresholds in children. The present study analyzes ABR thresholds across a large sample of children's ears obtained with both methods. The aim was to demonstrate the correlation between both methods using narrow band chirp and click stimuli.

Methods

Click and chirp evoked ABRs were measured in 253 children aged from 0 to 18 years to determine their individual auditory threshold. The delay-compensated stimuli were narrow band CE chirps with either 2000 Hz or 4000 Hz center frequencies. Measurements were performed consecutively during natural sleep, and under sedation or general anesthesia. Threshold estimation was performed for each measurement by two experienced audiologists.

Results

Pearson-correlation analysis revealed highly significant correlations (r = 0.94) between click and chirp derived thresholds for both 2 kHz and 4 kHz chirps. No considerable differences were observed either between different age ranges or gender. Comparing the thresholds estimated using ABR with click stimuli and chirp stimuli, only 0.8–2% for the 2000 Hz NB-chirp and 0.4–1.2% of the 4000 Hz NB-chirp measurements differed more than 15 dB for different degrees of hearing loss or normal hearing.

Conclusion

The results suggest that either NB-chirp or click ABR is sufficient for threshold estimation. This holds for the chirp frequencies of 2000 Hz and 4000 Hz. The use of either click- or chirp-evoked ABR allows a reduction of recording time in young infants. Nevertheless, to cross-check the results of one of the methods, we recommend measurements with the other method as well.     

Investigating the nonlinear microbubble response to chirp encoded, multipulse sequences

A modified Rayleigh-Plesset model was used to investigate the nonlinear acoustic response of ultrasound contrast microbubbles to multipulse phase and amplitude modulated, chirp encoded sequences. Trade-offs between the signal-to-noise ratio (SNR) and axial resolution were quantified for differing chirp time-bandwidth products and methods for minimising the artifacts formed in the postprocessing stages were developed. It was found that the chirp length can be increased and bandwidth reduced to improve SNR, though resolution is sacrificed. Results from the simulated chirp, pulse inverted, amplitude modulated (chirp PIAM) sequences were also compared with equivalent short pulse PIAM sequences and it was found that the chirp sequences preserve their extra energy after scattering, which translates to an improved SNR after processing. Compression artifacts were reduced by using chirps with a centre frequency and bandwidth tuned to the frequency response of the microbubble and reversing the frequency sweep of one chirp in the sequence. (E-mail: r.eckersley@imperial.ac.uk)