Double hearing protection and speech intelligibility-room for improvement

INTRODUCTION: Double hearing protection is used in many air forces around the world for protection in noisy aircraft environments, particularly in helicopters. The usual combination is foam ear plugs under headset or helmet muffs. Much of the research that spurred the introduction of foam earplugs indicated little change in speech intelligibility in persons with normal hearing. However, aircrew often complain about having to maximize intercom volume for speech understanding, causing a situation with no reserve volume and bad sound quality. In recent years, further developments have included so-called hi-fi plugs and custom made ear plugs which are claimed to improve speech communication. The aim of the present project was to investigate different types of ear plugs and their effect on speech intelligibility in helicopter noise. METHODS: Each of nine normal-hearing pilot subjects were placed in an environment of recorded helicopter noise from a BO-105 helicopter. Speech audiometry was performed under four different conditions: headset only, and three different ear plugs worn under the headset. Fitting of the ear plugs was performed by an ear, nose and throat specialist to ensure similar conditions. The sequence of test conditions was randomized and double-blind. In addition, a subjective rating scale was used. RESULTS: Wearing foam ear plugs under the headset decreased speech intelligibility dramatically. The "hi-fi" plug was somewhat better than foam plugs, and the custom made ear plug provided a speech intelligibility close to the headset-only situation. Subjective rating scores coincided with these findings. DISCUSSION: In helicopter noise, custom made ear plugs may provide a much improved speech intelligibility over conventional plugs when worn under a headset, while maintaining improved noise protection over the headset-alone situation. Custom made ear plugs might therefore be a good alternative to other forms of enhanced noise protection in helicopters.     

The relative impact of generic head-related transfer functions on auditory speech thresholds: implications for the design of three-dimensional audio displays

BACKGROUND: Auditory speech thresholds were measured in this study. METHODS: Subjects were required to discriminate a female voice recording of three-digit numbers in the presence of diotic speech babble. The voice stimulus was spatialized at 11 static azimuth positions on the horizontal plane using three different head-related transfer functions (HRTFs) measured on individuals who did not participate in this study. The diotic presentation of the voice stimulus served as the control condition. RESULTS: The results showed that two of the HRTFS performed similarly and had significantly lower auditory speech thresholds than the third HRTF. All three HRTFs yielded significantly lower auditory speech thresholds compared with the diotic presentation of the voice stimulus, with the largest difference at 60 degrees azimuth. CONCLUSION: The practical implications of these results suggest that lower headphone levels of the communication system in military aircraft can be achieved without sacrificing intelligibility, thereby lessening the risk of hearing loss.     

歼击机噪声对人听力及工效的影响

目的 研究歼击机噪声对人听力及工效的影响.方法 ①检查103名歼击机飞行员和62名地勤人员的听力.②测试18名歼-8D飞行员在飞机噪声暴露前、噪声暴露（40 min）后0.5 h、1.5 h和15 h的听力.③用汉语话音短语作为工效学指标,测试30名受试者在3种条件下,识听56个歼击机座舱显示信息汉语话音短语的成绩.结果①103名飞行员中,50名有高频听力损失（占48.5%）,16名有语频听力损失（占15.5%）;62名地勤人员中,43名有高频听力损失（占69.4%）,13名有语频听力损失（占21.0%）.飞行员和地勤人员高频听力损失的“V”型凹陷在6000 Hz.②飞机噪声对飞行员的暂时性听阈偏移有明显作用,噪声暴露后1.5 h,飞行员的暂时性听阈偏移有恢复的趋势,噪声暴露后15 h,飞行员的暂时性听阈偏移已有很大程度的恢复,但大部分频率的听力还未恢复至噪声暴露前水平.③30名受试者在3种条件下识听56个汉语话音短语的成绩：安静环境中佩戴无源耳罩最高,模拟飞机噪声环境中佩戴无源耳罩最低,模拟飞机噪声环境中佩戴有源耳罩居中,其差异均有显著性意义（P＜0.01）.结论 歼击机噪声大,能引起飞行员和地勤人员的听力损伤,并导致工作绩效下降.     

Speech intelligibility in aircraft noise as a function of altitude

Few studies have addressed physiological effects of altitude and noise combined, although these two factors are inherent parts of all aviation. Altitude effects on hearing function have mainly been studied using gas mixtures with reduced oxygen content. The results have been inconclusive. HYPOTHESIS: The present study was designed to assess the effect of altitude on speech intelligibility in aircraft noise. The primary hypothesis was that exposure to altitude would produce a detrimental, hypoxic effect on speech intelligibility in noise. METHODS: Eight male subjects with normal hearing were fitted with an aviation headset specially adapted for use with the audiometer. Pure-tone audiometry, as well as speech audiometry in noise, were performed at 0, 10,000, 13,000, and 16,000 ft simulated altitudes in a hypobaric chamber. The four test altitudes were performed double blind with respect to audiometry operator and test subject. Arterial blood gases where measured using an intra-arterial catheter. Tympanometric measurements verified full middle ear equilibration. Noise levels where monitored and logged throughout all experiments. RESULTS AND CONCLUSION: A substantial increase in speech intelligibility in noise due to altitude was evident in our study. The physical effect of barometric pressure on noise causing an increased signal-to-noise ratio was found to greatly outweigh any possible hypoxic detrimental effect.     

高强噪声环境中通话的语言可懂度

本研究应用高强噪声环境模拟系统,研究了四种噪声状态特性的送话实验和三种护耳器声衰减模型的听话实验,探讨了在高强噪声环境中通话的语言可懂度、影响因素及获得足够语言可懂度的条件.送话实验结果表明,语言可懂度不仅与噪声总声压级有关,而且与语言频段噪声声压级有关,噪声总声压级不超过125dB,语言频段噪声声压级不超过110dB时,语言可懂度可达95%以上.听话实验结果表明,听话语言可懂度与噪声声压级及护耳器声衰减的特性有关,当噪声总声压级为125dB,护耳器声衰减不低于模型3的数值时,听话语言可懂度也可达95%以上.     

Hearing and sound source identification with protective headwear

This study investigated the effect on hearing, sound attenuation, and sound source identification of a prototype neck and two prototype mandible guards attached to a combat helmet. Ten male subjects participated. Free-field hearing thresholds were measured from 250 Hz to 8,000 Hz with the head bare and fitted with the helmet alone and with the guards. Sound source identification was assessed using a horizontal array of eight loudspeakers surrounding the subject. The stimulus was a 75-dB SPL, 300-ms noise burst. Neither the helmet worn alone or with the guards affected hearing or provided significant sound attenuation. The helmet combinations resulted in a significant decrease in sound source identification, of 11.6%. This was due to diminished accuracy for loudspeakers close to the interaural axis of the head. The neck guard induced a frontal bias for these positions. This error pattern is not likely to interfere with localization during combat.     

Binaural speech discrimination under noise in hearing-impaired listeners

This study was undertaken to assess speech discrimination under binaural listening with background noise in hearing-impaired subjects. Subjects (58 sensori-neural, 23 conductive, and 19 mixed) were administered an indigenous version of W-22 PB words under: Condition I--Quiet--chamber noise below 28 dB with speech at 60 dB; and at a constant signal-to-noise (S/N) ratio of +10 dB with background white noise at 70 dB in Condition II and 80 dB in Condition III. The scores were a) 81 +/- 16%, b) 77 +/- 9%, and c) 79 +/- 13%. Mean scores decreased significantly (p less than 0.001) with noise in all groups while the score was more (p less than 0.001) at the higher noise level only in the sensori-neural group. The decrease in scores with advancing hearing impairment was less in noise than in quiet, probably due to binaural and satisfactory S/N ratio. The scores did not fall below 70% unless the handicap was marked. The need for suitable standards of binaural speech discrimination under noise in aircrew assessment is emphasized.     

Verbal communication in MR environments: effect of MR system acoustic noise on speech understanding

PURPOSE: To assess the masking effect of magnetic resonance (MR)-related acoustic noise and the effect of passive hearing protection on speech understanding. MATERIALS AND METHODS: Acoustic recordings were made at 1.5 T at patient and operator (interventionalist in the MR suite) locations for relevant pulse sequences. In an audiologic laboratory, speech-to-noise ratios (STNRs) were determined, defined as the difference between the absolute sound pressure levels of MR noise and speech. The recorded noise of the MR sequences was played simultaneously with the recorded sentences at various intensities, and 15 healthy volunteers (seven women, eight men; median age, 27 years) repeated these sentences as accurately as possible. The STNR that corresponded with a 50% correct repetition was used as the measure for speech intelligibility. In addition, the effect of passive hearing protection on speech intelligibility was tested by using an earplug model. RESULTS: Overall, speech understanding was reduced more at operator than at patient location. Most problematic were fast gradient-recalled-echo train and spiral k-space sequences. As the absolute sound pressure level of these sequences was approximately 100 dB at patient location, the vocal effort needed to attain 50% intelligibility was shouting (>77 dB). At operator location, less effort was required because of the lower sound pressure levels of the MR noise. Fast spoiled gradient-recalled-echo and echo-planar imaging sequences showed relatively favorable results with raised voice at operator location and loud speaking at patient location. The use of hearing protection slightly improved STNR. CONCLUSION: At 1.5 T, the level of MR noise requires that large vocal effort is used, at the operator and especially at the patient location. Depending on the specific MR sequence used, loud speaking or shouting is needed to achieve adequate bidirectional communication with the patient. The wearing of earplugs improves speech intelligibility.     

Speech intelligibility in noise using throat and acoustic microphones

INTRODUCTION: Helicopter cockpits are very noisy and this noise must be reduced for effective communication. The standard U.S. Army aviation helmet is equipped with a noise-canceling acoustic microphone, but some ambient noise still is transmitted. Throat microphones are not sensitive to air molecule vibrations and thus, transmittal of ambient noise is reduced. It is possible that throat microphones could enhance speech communication in helicopters, but speech intelligibility with the devices must first be assessed. In the current study, speech intelligibility of signals generated by an acoustic microphone, a throat microphone, and by the combined output of the two microphones was assessed using the Modified Rhyme Test (MRT). METHODS: Stimulus words were recorded in a reverberant chamber with ambient broadband noise intensity at 90 and 106 dBA. Listeners completed the MRT task in the same settings, thus simulating the typical environment of a rotary-wing aircraft. RESULTS: Results show that speech intelligibility is significantly worse for the throat microphone (average percent correct = 55.97) than for the acoustic microphone (average percent correct = 69.70), particularly for the higher noise level. In addition, no benefit is gained by simultaneously using both microphones. A follow-up experiment evaluated different consonants using the Diagnostic Rhyme Test and replicated the MRT results. DISCUSSION: The current results show that intelligibility using throat microphones is poorer than with the use of boom microphones in noisy and in quiet environments. Therefore, throat microphones are not recommended for use in any situation where fast and accurate speech intelligibility is essential.     

低压舱内大鼠游泳运动模型的建立

目的：大鼠在低压舱内进行游泳时,皮毛上会附着大量气泡,严重影响对大鼠运动能力的判断。本实验旨在建立低压舱内稳定可靠的大鼠游泳运动模型。方法：SD大鼠分平原组和高原组,每组大鼠又分为A、B、C、D四组。A组大鼠为对照组;B组大鼠在游泳用水中加入去污剂;C组大鼠实验前1天用脱毛剂脱去头部以下被毛;D组大鼠用实验前1天沸腾后自然冷却的水游泳。大鼠分别置于平原和5 000m低压舱内饲养,24h后各组在其饲养环境下进行负重2.5%体重的游泳运动。观察大鼠游泳运动情况,并记录游泳力竭时间。结果：在平原,往游泳用水中加入吐温20（B组）或去除大鼠被毛（C组）可减轻大鼠身上附着的气泡,而在低压舱中使用这两种方法无效。无论是在舱内还是在舱外,使用实验前1天沸腾后自然冷却的水（D组）可完全消除大鼠游泳时皮毛上附着的气泡。D组大鼠在平原力竭时间为（56±11）min,显著长于高原力竭时间（25±17）min。结论：通过实验前煮沸游泳用水,可消除大鼠在低压舱中游泳时皮毛上附着的气泡,建立稳定可靠的低压舱内大鼠游泳运动模型。     

CT differentiation of pleural effusion from ascites. An evaluation of four signs using blinded analysis of 52 cases

Four criteria have been described to differentiate ascites from pleural effusion by computed tomography (CT). These four signs (the diaphragm sign, the displaced crus sign, the interface sign, and the bare area sign) were compared in a retrospective blinded analysis in 52 patients with ascites, right pleural effusion, or both ascites and right pleural effusion. There were limitations with each of the four criteria. Each of the individual criteria was reliable when only one abnormal fluid collection, either pleural effusion or ascites, was present. When both a right pleural effusion and ascites were present, none of the four criteria reliably identified both fluid collections. The combined use of the four criteria, however, led to a correct identification of all the abnormal fluid collections.     

Is terminology used effectively to convey diagnostic certainty in radiology reports?

RATIONALE AND OBJECTIVES: This study was performed to assess the extent of agreement among radiologists and nonradiologists in perception of diagnostic certainty conveyed by words and phrases commonly used in radiology reports. MATERIALS AND METHODS: The study was performed in a large academic radiology department. To determine the commonly used terminology for conveying diagnostic certainty in radiology reports, 12 randomly selected radiologists from six different subspecialties were interviewed. The authors identified the 15 most commonly used words and phrases and included these in random order in a questionnaire sent to all staff radiologists (n = 45) and to 158 referring physicians. Physicians were asked to rank the 15 phrases in order of the diagnostic certainty conveyed by each, from 1 (most certain) to 15 (least certain), using each number only once. The kappa statistic was used to assess agreement in rank order among physicians. RESULTS: The questionnaire response rate was 76% (n = 34) for radiologists and 49% (n = 78) for nonradiologists. There was excellent agreement among radiologists (kappa = 0.95) and nonradiologists (kappa = 0.93) in the rank order for the phrase diagnostic of. Although there was good agreement (kappa = 0.45) among radiologists for the word unlikely, agreement among nonradiologists was poor (kappa = 0.27). There was very poor agreement among all physicians for the rank order of the other 13 phrases. CONCLUSION: Among radiologists and nonradiologists, concordance was poor regarding the diagnostic certainty associated with phrases commonly used in radiology reports. Because poor agreement could lead to suboptimal quality of care, the standardization of terminology would benefit all parties.     

Robust estimation of spatially variable noise fields

Consideration of spatially variable noise fields is becoming increasingly necessary in MRI given recent innovations in artifact identification and statistically driven image processing. Fast imaging methods enable study of difficult anatomical targets and improve image quality but also increase the spatial variability in the noise field. Traditional analysis techniques have either assumed that the noise is constant across the field of view (or region of interest) or have relied on separate MRI acquisitions to measure the noise field. These methods are either inappropriate for many modern scanning protocols or are overly time‐consuming for already lengthy scanning sessions. We propose a new, general framework for estimating spatially variable noise fields from related, but independent MR scans that we call noise field equivalent scans. These heuristic analyses enable robust noise field estimation in the presence of artifacts. Generalization of noise estimators based on uniform regions, difference images, and maximum likelihood are presented and compared with the estimators derived from the proposed framework. Simulations of diffusion tensor imaging and T₂‐relaxometry demonstrate a 10‐fold reduction in mean squared error in noise field estimation, and these improvements are shown to be robust to artifact contamination. In vivo studies show that spatially variable noise fields can be readily estimated with typical data acquired at 1.5T. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Perirenal lucency ("kidney sweat"): a new sign of renal failure.

OBJECTIVE: This study describes a new sonographic finding in renal failure: perirenal lucency, which we call the "kidney sweat" sign. MATERIALS AND METHODS: During 1 year at our institution, 502 renal sonograms were obtained. Sonography evaluated 330 patients with renal failure. All of the examinations were retrospectively analyzed. RESULTS: An extracapsular hypoechoic rim was present in 47 (14%) of the 330 patients with renal failure. The finding, when present, was always bilateral. The hypoechoic rim was not present in the remaining 283 patients with renal failure. Forty (85%) of the 47 patients had kidneys that were hyperechoic compared with the liver. Twenty-eight (60%) of the 47 patients had kidneys that were hyperechoic compared with the spleen. In 15 (32%) of the 47 patients, the kidneys were small. Ascites was present in 11 (23%) of the 47 patients. Of the 283 patients with renal failure whose sonograms did not show the hypoechoic rim, 76 patients had normal sonographic findings. The remaining 207 patients with renal failure who did not show the kidney sweat sign had hydronephrosis, stones, cysts, echogenic kidneys, small kidneys, or ascites. CONCLUSION: An extracapsular hypoechoic rim is found in patients with renal failure. We call this finding "kidney sweat." We believe, but cannot currently prove, that the kidney sweat sign represents edema. It is an additional sonographic finding in patients with renal failure.     

胃溃疡的相关特殊X线征象分析

目的:分析胃溃疡的特殊X线表现,提高对胃溃疡特殊X线表现的认识和诊断水平。方法:回顾性分析8例具有特殊X线征象胃溃疡的X线资料,病例均经病理活检或手术证实。结果:本组病例全部是良性胃溃疡,由于其具有酷似恶性胃溃疡的特殊X线征象,故诊断正确率低:明确诊断1例,疑似诊断3例,误诊4例。结论:通过对胃溃疡X线征象的充分分析与随访观察,可以提高对胃溃疡特殊X线表现的认识能力。     

汉语语音告警的工效学研究

为探讨航天器在噪声背景下汉语语音告警适宜参数的选择，采用自行建立的“语音报警工效学模拟与分析系统”，对４０名视、听正常的健康男性，进行了双重作业下的载人航天器报警用语听觉反应时实验以及主告警音适宜时长主观评定实验，并从听觉反应时、认知特性以及报警对作业负荷的影响等几方面对航天器汉语语音告警适宜参数的选择进行了分析。结果显示：主告警音时长０．３５￣０．５５ｓ、主间隔０．１５￣０．３５ｓ、语速４￣６字     

咽扩约肌成形术治疗腭咽闭合不全临床研究

目的　了解咽扩约肌成形术对腭裂术后腭咽闭合不全的治疗作用。方法　选择腭裂修复术后 1年以上 ,经语音训练仍有语言障碍 ,分别令其朗读《汉语腭裂字表》同时录音 ,然后 7名听力语音正常的医护人员试听录音并计算正确率 ,正确率在 70 %以下患者 3 0例 ,分别行咽扩约肌成形术治疗。结果　术前语音正常 0人 ,基本正常 0人 ,中度发音异常1 1人 ,明显发音异常 1 4人 ,严重发音异常 5人。术后语音正常 1 6人 ,基本正常 1 1人 ,中度发音异常 2人 ,明显发音异常1人 ,严重发音异常 0人。结论　咽扩约肌成形术能使腭裂术后仍有腭咽闭合不全患者语音明显改善。     

Computer-aided diagnosis of pulmonary nodules: results of a large-scale observer test

PURPOSE: To determine the frequency on magnetic resonance (MR) images of a widened pericholecystic space, which the authors call the expanded gallbladder fossa sign, and to assess the sensitivity and specificity of this sign for cirrhosis. MATERIALS AND METHODS: Three-hundred thirteen patients who underwent MR imaging were included in this study, including 190 with pathologically proved cirrhosis (cirrhosis patients) and 123 without history of chronic liver diseases (control subjects). MR images were qualitatively evaluated by three independent observers for the presence of the expanded gallbladder fossa sign. This sign was considered present if there was enlargement of the pericholecystic space (i.e., gallbladder fossa) and the space was bounded laterally by the edge of the right hepatic lobe and medially by the edge of the left lateral segment, in conjunction with nonvisualization of the left medial segment. RESULTS: The expanded gallbladder fossa sign was seen in 129 cirrhosis patients and in three control subjects (P < .001). The sensitivity, specificity, accuracy, and positive predictive value of this sign for the MR diagnosis of cirrhosis were 68%, 98%, 80%, and 98%, respectively. CONCLUSION: The expanded gallbladder fossa sign on MR images is a frequently present, specific indicator of cirrhosis. This sign can be used as a simple and highly specific sign of cirrhosis, if present, despite the overall sensitivity of 68%.     

Synthetic speech and its perception in complex acoustic conditions

Perception of synthetic speech in noise conditions has certain specific features which largely determine noise resistance of synthetic verbal communication. On the one hand, noise resistance of synthetic speech is lower than that of natural speech. This has been demonstrated by the study of the masking effect of 90 and 100 dB noise on natural and synthetic speech. On the other hand, there are methods of speech synthesis that seem very promising. Phonetic analysis of natural and synthetic syllables has shown that noise resistance of synthetic syllables is higher than that of natural syllables but perception of blended speech displays an inverse correlation. This demonstrates the fact that perception of verbal signals under noise conditions is based on the sensory relations that differ from those simulated by synthetic communication.