Risk of noise-induced hearing loss due to recreational sound: Review and recommendations.

This review was conducted to address three questions related to recreational sound exposure: (1) what criteria are used to determine noise exposure limits, (2) are there differences in the risk of hearing loss from occupational noise versus recreational sound, and (3) what is an appropriate exposure limit for recreational sound? For the first question, most standards specify an 8-h occupational noise exposure limit (LEX) of 85 dBA. This limit assumes that some workers exposed at the limit will develop hearing loss. To eliminate the risk of hearing loss, a 24-h equivalent continuous level (LEQ24h) limit of 70 dBA is appropriate. For the second question, there is some evidence that the effects of occupational noise on hearing may be worse than energetically equivalent recreational sound. Limits developed for noise are nevertheless applicable to recreational sound, and use of existing statistical models to predict hearing loss from recreational sound is appropriate, with the caveat that these models are limited to durations ≤40 years. For the third question, a recreational sound limit of 80 dBA LEX, equivalent to a 75 dBA LEQ24h, will virtually eliminate the risk of recreationally induced hearing loss in adults. Lower limits may be warranted for vulnerable or susceptible individuals.

Pediatric Ototoxicity: Current Trends and Management.

Medical interventions to combat serious infection or malignancies carry significant morbidities, including ototoxicity. While these lifesaving drugs are often necessary to preserve life, the impact on quality of life for survivors is increasingly concerning for families and healthcare providers. Of primary importance for medical prescribers are appropriately sensitive ototoxicity grading scales and audiological monitoring protocols for surveillance for hearing loss. The intent of grading scales is to help communicate complicated audiological information to non-audiologist healthcare providers (such as oncologists) to help them make good decisions with regards to chemotherapy dosing. Appropriate audiological monitoring helps reduce the time delay between the adventitious onset of hearing loss and the diagnosis and intervention. Finally, pediatric ototoxicity grading and monitoring protocols help ensure timely access to adequate hearing habilitation, verification and validation of the management of permanent medication-induced hearing loss and tinnitus in children.

Risk Factors for Hearing Loss in Patients with Cystic Fibrosis.

BACKGROUND: Patients with cystic fibrosis (CF) are at increased risk for sensorineural hearing loss (SNHL) due, at least in part, to the ototoxic side effects of routine CF therapies. However, the prevalence of SNHL and additional factors contributing to the development of SNHL are unknown. PURPOSE: To identify risk factors associated with the development of SNHL in a large cohort of CF patients who had been referred for audiometric testing. RESEARCH DESIGN: A retrospective study of audiometric results and medication information in a cohort of patients with CF. STUDY SAMPLE: Records of 178 CF patients seen at Boston Children's Hospital for audiometric testing from 2007 to 2010 were reviewed. Mean age of patients was 18 yr (standard deviation = 10 yr), and 98 (55%) of the patients were female. DATA COLLECTION AND ANALYSIS: Audiometric results, medications, and hospitalizations were recorded. Multivariable logistic regression was used to evaluate the association between SNHL and the number of hospitalizations and chronic antibiotic use in the year prior to the patients' audiometry. RESULTS: In this sample, 37/178 (21%) patients had SNHL. Twenty-nine (78%) of the 37 patients had bilateral SNHL and 8 (22%) had unilateral SNHL. Across all age groups, the majority of patients had a bilateral hearing loss (HL). A multivariable model showed that older age and more frequent hospitalizations were associated with SNHL. The number of courses of chronic antibiotics in the year prior to audiometric testing was not correlated with rate of HL. CONCLUSIONS: This study suggests that age and frequency of hospitalizations are key predictors of HL development. Increased awareness and regular screening for SNHL should be included in the routine care of CF patients, particularly those at the highest risk.

Sensorineural hearing loss in congenital diaphragmatic hernia survivors is associated with postnatal management and not defect size.

BACKGROUND/PURPOSE: We determined the incidence of sensorineural hearing loss (SNHL; >20dB at any frequency) in a contemporary cohort of congenital diaphragmatic hernia (CDH) survivors at a single tertiary care center and identified potential risk factors for SNHL. METHODS: From 2000 through 2011, clinical and audiologic data were collected on 122 surgically-repaired Bochdalek CDH patients. CDH defect size, duration of ventilation, and cumulative aminoglycoside treatment were used for multivariate logistic regression. RESULTS: Incidence of SNHL was 7.4% (9/122). We identified one significant independent predictor of SNHL: cumulative length of aminoglycoside treatment (P<.001; OR 1.44, 95% CI: 1.13-1.83). CONCLUSIONS: Over the last decade, the incidence of SNHL in our CDH patients is low compared to previous reports in the literature (7.4%) and is not associated with CDH defect size or the need for extracorporeal membrane oxygenation. Prolonged duration of aminoglycoside treatment increases the risk of SNHL independent of defect size and duration of ventilation.

Cultural and demographic factors influencing noise exposure estimates from use of portable listening devices in an urban environment.

PURPOSE: This study examined listening levels and duration of portable listening devices (PLDs) used by people with diversity of ethnicity, education, music genre, and PLD manufacturer. The goal was to estimate participants' PLD noise exposure and identify factors influencing user behavior. METHOD: This study measured listening levels of 160 adults in 2 New York City locations: (a) a quiet college campus and (b) Union Square, a busy interchange. Participants completed a questionnaire regarding demographics and PLD use. Ordinary least squares regression was used to explore the significance of demographic and behavioral factors. RESULTS: Average listening level was 94.1 dBA, with 99 of 160 (61.9%) and 92 of 159 (57.5%) exceeding daily (L A8hn) and weekly (L Awkn) recommended exposure limit, respectively. African American participants listened at the highest average levels (99.8 dBA). CONCLUSIONS: A majority of PLD users exceeded recommended exposure levels. Factors significant for higher exposure were ethnicity and age; factors not significantly associated with exposure were gender, education, location, awareness of possible association between PLD use and noise-induced hearing loss, mode of transportation, device manufacturer, and music genre. Efforts to effect behavior changes to lessen noise-induced hearing loss risk from PLD use should be sensitive to the cultural differences within the targeted population.

Portable music player users: cultural differences and potential dangers.

Many studies have examined the use of portable music players portable listening devices (PLDs) from various ethnic groups. Some findings suggest that there may be differences among ethnic groups that lead to louder or longer listening when using PLD devices. For example, some studies found that Hispanic PLD users listen at higher volume levels while other studies found that African American PLD users listen at higher volume levels. No investigator has explained the reasons for differences among ethnic groups in listening intensity. This paper will address the possible reasons for these differences and offer guidelines for the prevention of noise-induced hearing loss.

Clinical trial of a farnesyltransferase inhibitor in children with Hutchinson-Gilford progeria syndrome.

Hutchinson-Gilford progeria syndrome (HGPS) is an extremely rare, fatal, segmental premature aging syndrome caused by a mutation in LMNA that produces the farnesylated aberrant lamin A protein, progerin. This multisystem disorder causes failure to thrive and accelerated atherosclerosis leading to early death. Farnesyltransferase inhibitors have ameliorated disease phenotypes in preclinical studies. Twenty-five patients with HGPS received the farnesyltransferase inhibitor lonafarnib for a minimum of 2 y. Primary outcome success was predefined as a 50% increase over pretherapy in estimated annual rate of weight gain, or change from pretherapy weight loss to statistically significant on-study weight gain. Nine patients experienced a ≥50% increase, six experienced a ≥50% decrease, and 10 remained stable with respect to rate of weight gain. Secondary outcomes included decreases in arterial pulse wave velocity and carotid artery echodensity and increases in skeletal rigidity and sensorineural hearing within patient subgroups. All patients improved in one or more of these outcomes. Results from this clinical treatment trial for children with HGPS provide preliminary evidence that lonafarnib may improve vascular stiffness, bone structure, and audiological status.

Platinum-induced ototoxicity in children: a consensus review on mechanisms, predisposition, and protection, including a new International Society of Pediatric Oncology Boston ototoxicity scale.

PURPOSE: The platinum chemotherapy agents cisplatin and carboplatin are widely used in the treatment of adult and pediatric cancers. Cisplatin causes hearing loss in at least 60% of pediatric patients. Reducing cisplatin and high-dose carboplatin ototoxicity without reducing efficacy is important. PATIENTS AND METHODS: This review summarizes recommendations made at the 42nd Congress of the International Society of Pediatric Oncology (SIOP) in Boston, October 21-24, 2010, reflecting input from international basic scientists, pediatric oncologists, otolaryngologists, oncology nurses, audiologists, and neurosurgeons to develop and advance research and clinical trials for otoprotection. RESULTS: Platinum initially impairs hearing in the high frequencies and progresses to lower frequencies with increasing cumulative dose. Genes involved in drug transport, metabolism, and DNA repair regulate platinum toxicities. Otoprotection can be achieved by acting on several these pathways and generally involves antioxidant thiol agents. Otoprotection is a strategy being explored to decrease hearing loss while maintaining dose intensity or allowing dose escalation, but it has the potential to interfere with tumoricidal effects. Route of administration and optimal timing relative to platinum therapy are critical issues. In addition, international standards for grading and comparing ototoxicity are essential to the success of prospective pediatric trials aimed at reducing platinum-induced hearing loss. CONCLUSION: Collaborative prospective basic and clinical trial research is needed to reduce the incidence of irreversible platinum-induced hearing loss, and optimize cancer control. Wide use of the new internationally agreed-on SIOP Boston ototoxicity scale in current and future otoprotection trials should help facilitate this goal.

"Accelerated ear-age": a new measure of chemotherapy-induced ototoxicity.

Currently, there are several different scales that grade chemotherapy-induced ototoxicity. This report highlights how the implications of the conclusions drawn from each scale differ and compare these prior scales to a more functionally based scale developed at Children's Hospital Boston. Additionally, this report introduces the concept of "ear-age," akin to the age at which one would expect the observed decrease in hearing as a consequence of normative aging (but documented in a child or young adult following chemotherapy).

Pediatric hearing assessment by auditory brainstem response in the operating room.

OBJECTIVES: To investigate the factors contributing to the discrepancies between auditory brainstem response (ABR) thresholds obtained in the operating room (OR) and hearing outcomes obtained in the follow-up period and to explore the benefits and limitations of performing ABR in the OR. METHODS: A retrospective review study was conducted in a pediatric tertiary care facility. A total of 116 patients were identified with complete records, including OR-ABR results, medical examination and surgical procedure notes, and follow-up medical/audiological evaluation. Patients were divided into three groups: (1) 58 patients with middle ear effusion underwent myringotomy and tube placement, (2) 12 patients underwent myringotomy without tube placement, (3) 46 patients underwent ear examination only without effusion found. OR-ABR results were compared to audiological follow-up evaluations and analyzed for each group. RESULTS: In patients with middle ear effusion and tube placement, the average threshold difference between OR-ABR and follow-up audiological evaluation was 9.7 dB (± 12.7), with highest discrepancy of 45 dB. On the other hand, in patients with dry ears and/or no tube placement, the average threshold difference was only 3.8 dB (± 8.6). Moreover, the discrepancy was more prominent in patients with mucoid effusion and larger at lower frequency, i.e., 1000 Hz. CONCLUSIONS: The hearing thresholds estimated by ABR testing in the OR can be elevated and follow-up hearing evaluation after tube placement is needed. While ABR testing is valuable in the assessment of pediatric patients, especially for children who are difficult-to-test or have complicated medical conditions, caution should be taken when interpreting OR-ABR results.

Noise exposure estimates of urban MP3 player users.

PURPOSE: To examine the sound level and duration of use of personal listening devices (PLDs) by 189 college students, ages 18-53 years, as they entered a New York City college campus, to determine whether noise exposure from PLDs was in excess of recommended exposure limits and what factors might influence exposure. METHOD: Free-field equivalent sound levels from PLD headphones were measured on a mannequin with a calibrated sound level meter. Participants reported demographic information, whether they had just come off the subway, the type of PLD and earphones used, and duration per day and days per week they used their PLDs. RESULTS: Based on measured free-field equivalent sound levels from PLD headphones and the reported PLD use, per day 58.2% of participants exceeded 85 dB A-weighted 8-hr equivalent sound levels (L(Aeq)), and per week 51.9% exceeded 85 dB A-weighted 40-hr equivalent continuous sound levels (L(Awkn)). CONCLUSIONS: The majority of PLD users exceeded recommended sound exposure limits, suggesting that they were at increased risk for noise-induced hearing loss. Analyses of the demographics of these participants and mode of transportation to campus failed to indicate any particular gender differences in PLD use or in mode of transportation influencing sound exposure.

Teenage use of portable listening devices: a hazard to hearing?

BACKGROUND: Recently, a number of popular media articles have raised some concern that portable listening devices (PLDs) may be increasing the risk for music-induced hearing loss (MIHL). However, literature regarding adolescents' listening behavior and how their attitudes and beliefs relate to behavior is currently limited. PURPOSE: The purposes of this study were (1) to investigate the relationship between volume control settings and output levels of PLDs, (2) to examine how adolescents' listening behavior changes as a function of background noise and noise isolation, (3) to investigate the relationship between self-reported listening levels and laboratory-measured listening levels, and (4) to evaluate the validity of the Listening Habits Questionnaire as a research tool for evaluating how attitudes and beliefs relate to PLD use behavior. RESEARCH DESIGN: A descriptive study. Experiment 1 evaluated the output levels of a set of PLDs, and Experiment 2 characterized the listening behavior and attitudes toward PLD use of a group of adolescents. STUDY SAMPLE: Twenty-nine adolescents aged 13-17 yr, with normal hearing, participated in Experiment 2. DATA COLLECTION AND ANALYSIS: Experiment 1 evaluated the output levels of a set of PLDs with stock and accessory earphones using an acoustic manikin. Experiment 2 included survey measures of listening behavior and attitudes as well as output levels measured using a probe microphone. CONCLUSIONS: The output levels of PLDs are capable of reaching levels that could increase the risk for MIHL, and 14% of teenagers in this study reported behavior that puts them at increased risk for hearing loss. However, measured listening levels in the laboratory settings did not correlate well with self-reported typical listening levels. Further, the Listening Habits Questionnaire described in this study may provide a useful research tool for examining the relationship between attitudes and beliefs and listening behavior.

Audiologic phenotype and progression in GJB2 (Connexin 26) hearing loss.

OBJECTIVES: To document the audiologic phenotype of children with biallelic GJB2 (connexin 26) mutations, and to correlate it with the genotype. DESIGN: Prospective, observational study. SETTING: Tertiary care children's hospital. PATIENTS: Infants and children with sensorineural hearing loss (SNHL). INTERVENTION: Sequencing of the GJB2 (connexin 26) gene. MAIN OUTCOME MEASURES: Degree and progression of SNHL. RESULTS: From December 1, 1998, through November 30, 2006, 126 children with biallelic GJB2 mutations were identified. Of the 30 different mutations identified, 13 (43%) were truncating and 17 (57%) were nontruncating; 62 patients had 2 truncating, 30 had 1 truncating and 1 nontruncating, and 17 had 2 nontruncating mutations. Eighty-four patients (67%) initially had measurable hearing in the mild to severe range in at least 1 of 4 frequencies (500, 1000, 2000, or 4000 Hz). Of these 84 patients with residual hearing, 47 (56%) had some degree of progressive hearing loss. Patients with 2 truncating mutations had significantly worse hearing compared with all other groups. Patients who had 1 or 2 copies of either an M34T or a V37I allele had the mildest hearing loss. CONCLUSIONS: Hearing loss owing to GJB2 mutations ranges from mild to profound and is usually congenital. More than 50% of patients will experience some hearing loss progression, generally gradually but occasionally precipitously. Hearing loss severity may be influenced by genetic factors, such as the degree of preserved protein function in nontruncating mutations, whereas hearing loss progression may be dependent on factors other than the connexin 26 protein. Genetic counseling for patients with GJB2 mutations should include the variable audiologic phenotype and the possibility of progression.

Sensorineural hearing loss in patients with cystic fibrosis.

OBJECTIVE: To determine the prevalence of sensorineural hearing loss (SNHL) in cystic fibrosis (CF) patients and its relationship to antibiotic use. STUDY DESIGN: Case series with chart review. SETTING: Tertiary care pediatric hospital. SUBJECTS AND METHODS: We reviewed the medical records of CF patients seen in our children's hospital between March 1994 and December 2007. Data collected included patient demographics, audiograms, tympanograms, genotype, and use of potentially ototoxic antibiotics. RESULTS: Seven of 50 (14%) patients had SNHL. Three percent of patients who received 10 courses (P<0.01). No patients who received five or fewer courses of nasal irrigation with aminoglycosides had SNHL versus 23 percent of those who received more than five courses (P<0.05). Nine percent of patients who received five or fewer courses of macrolides had SNHL versus 60 percent of those who received more than five courses (P=0.079). CONCLUSION: CF patients receiving aminoglycosides are at high risk for developing SNHL.

Ototoxicity in children treated for osteosarcoma.

BACKGROUND: Cisplatin is an effective agent against osteosarcoma. Ototoxicity from osteosarcoma treatment protocols has not been well defined. The aim of this study was to determine the incidence and risk factors for hearing loss in children treated for osteosarcoma. PROCEDURE: Eligible patients had osteosarcoma diagnosed and treated at the Dana-Farber Cancer Institute/Children's Hospital Boston from January 1, 1995 to December 12, 2004, were 3-18 years of age at diagnosis, and had a normal audiogram prior to the start of chemotherapy. Patients received cisplatin according to the standard practice or current open protocol. Patients who developed hearing loss during treatment had cisplatin held on an individualized basis. Hearing function was evaluated prior to the start of therapy, before each cycle, and off-therapy. Fisher's exact test and logistic regression models were used to identify univariate and independent predictors of hearing loss, respectively. RESULTS: Seven out of nine patients (78%) who received cisplatin 120 mg/m(2)/day on 1 day developed hearing loss compared to 8/27 (30%) who received 60 mg/m(2)/day for 2 days (P = 0.019). Logistic regression showed that age, cumulative cisplatin dose, and administration of cisplatin 120 mg/m(2)/day were independent predictors of hearing loss. Cisplatin administered as 60 mg/m(2)/day for 2 days resulted in a low incidence (30%) of any hearing loss and a very low incidence (4%) of educationally significant hearing loss. CONCLUSIONS: Cisplatin administered as 60 mg/m(2)/day for 2 days resulted in a low incidence of significant hearing loss. These results suggest that cisplatin as 120 mg/m(2)/day be avoided due to an unacceptable incidence of hearing loss.

Factors associated with sensorineural hearing loss among survivors of extracorporeal membrane oxygenation therapy.

OBJECTIVES: To endeavor to explain why some graduates of extracorporeal membrane oxygenation (ECMO) therapy develop sensorineural hearing loss (SNHL) whereas others do not, to study the variability seen in the degree of SNHL, to attempt to explain why some graduates with SNHL experience progressive worsening whereas others do not, and to describe the time course of the onset of SNHL on the basis of identified risk factors. DESIGN: A retrospective chart review with proportional-hazards regression analysis to identify specific risk factors for SNHL from a list of patient and treatment variables. SETTING: Children's Hospital Boston, a pediatric tertiary-care facility and ECMO center. PATIENTS: Neonatal ECMO graduates born in 1986-1994 who survived to discharge and underwent audiologic evaluations (n = 111) and a random sample of ECMO graduates who survived to discharge and did not undergo audiologic evaluations (n = 30). OUTCOME MEASURES: Audiologic data, including the presence or absence of SNHL, the severity of SNHL at the most recent evaluation, the stability or progressive worsening of hearing (with the first evaluation compared with the most recent evaluation), and the occurrence of delayed-onset SNHL. RESULTS: Twenty-nine (26%) of 111 ECMO graduates who underwent audiologic testing had SNHL at the last evaluation. Of these 29 subjects with SNHL, 21 (72%) had progressive SNHL, of whom 14 (48%) had delayed-onset SNHL. The age of identification of SNHL ranged from 4 months to 8 years 11 months. Factors identified with proportional-hazards regression analyses as being associated significantly with the time to onset of SNHL were a primary diagnosis of congenital diaphragmatic hernia (hazard ratio: 2.60), length of ECMO therapy (hazard ratio: 7.18), and number of days children received aminoglycoside antibiotics (hazard ratio: 5.56). Kaplan-Meier "time-to-event" curves were constructed to illustrate the time course of onset of SNHL, as affected by each of the variables identified as significant risk factors. CONCLUSIONS: These findings illustrate the need for early, routine, audiologic evaluations throughout childhood for all ECMO graduates. Children at even greater risk for developing SNHL because of a history of congenital diaphragmatic hernia, prolonged ECMO therapy, and/or a lengthy course of aminoglycoside antibiotic therapy should be monitored even more closely throughout childhood, depending on the child's individual risk indicators, as suggested here. On the basis of these risk indicators, efforts can be made to minimize the risk of hearing loss while a child is being treated with ECMO. In addition, these risk indicators can assist with counseling families of ECMO graduates regarding the child's specific risk of developing SNHL and how it can be managed should it occur.

Output levels of commercially available portable compact disc players and the potential risk to hearing.

OBJECTIVE: To measure the sound levels generated by the headphones of commercially available portable compact disc players and provide hearing healthcare providers with safety guidelines based on a theoretical noise dose model. DESIGN: Using a Knowles Electronics Manikin for Acoustical Research and a personal computer, output levels across volume control settings were recorded from headphones driven by a standard signal (white noise) and compared with output levels from music samples of eight different genres. Many commercially available models from different manufacturers were investigated. Several different styles of headphones (insert, supra-aural, vertical, and circumaural) were used to determine if style of headphone influenced output level. RESULTS: Free-field equivalent sound pressure levels measured at maximum volume control setting ranged from 91 dBA to 121 dBA. Output levels varied across manufacturers and style of headphone, although generally the smaller the headphone, the higher the sound level for a given volume control setting. Specifically, in one manufacturer, insert earphones increased output level 7-9 dB, relative to the output from stock headphones included in the purchase of the CD player. In a few headphone-CD player combinations, peak sound pressure levels exceeded 130 dB SPL. CONCLUSIONS: Based on measured sound pressure levels across systems and the noise dose model recommended by National Institute for Occupational Safety and Health for protecting the occupational worker, a maximum permissible noise dose would typically be reached within 1 hr of listening with the volume control set to 70% of maximum gain using supra-aural headphones. Using headphones that resulted in boosting the output level (e.g., insert earphones used in this study) would significantly decrease the maximum safe volume control setting; this effect was unpredictable from one manufacturer to another. In the interest of providing a straightforward recommendation that should protect the hearing of the majority of consumers, reasonable guidelines would include a recommendation to limit headphone use to 1 hr or less per day if using supra-aural style headphones at a gain control setting of 60% of maximum.

Informational masking and musical training.

The relationship between musical training and informational masking was studied for 24 young adult listeners with normal hearing. The listeners were divided into two groups based on musical training. In one group, the listeners had little or no musical training; the other group was comprised of highly trained, currently active musicians. The hypothesis was that musicians may be less susceptible to informational masking, which is thought to reflect central, rather than peripheral, limitations on the processing of sound. Masked thresholds were measured in two conditions, similar to those used by Kidd et al. [J. Acoust. Soc. Am. 95, 3475-3480 (1994)]. In both conditions the signal was comprised of a series of repeated tone bursts at 1 kHz. The masker was comprised of a series of multitone bursts, gated with the signal. In one condition the frequencies of the masker were selected randomly for each burst; in the other condition the masker frequencies were selected randomly for the first burst of each interval and then remained constant throughout the interval. The difference in thresholds between the two conditions was taken as a measure of informational masking. Frequency selectivity, using the notched-noise method, was also estimated in the two groups. The results showed no difference in frequency selectivity between the two groups, but showed a large and significant difference in the amount of informational masking between musically trained and untrained listeners. This informational masking task, which requires no knowledge specific to musical training (such as note or interval names) and is generally not susceptible to systematic short- or medium-term training effects, may provide a basis for further studies of analytic listening abilities in different populations.

Functional role of the human inferior colliculus in binaural hearing.

Psychophysical experiments were carried out in a rare case involving a 48 year old man (RJC) with a small traumatic hemorrhage of the right dorsal midbrain, including the inferior colliculus (IC). RJC had normal audiograms bilaterally, but there was a marked decrease in wave V amplitude on click-evoked brainstem auditory evoked potentials following left ear stimulation. RJC demonstrated a deficit in sound localization identification when the loudspeakers lay within the auditory hemifield contralateral to his IC lesion. Errors showed a consistent bias towards the hemifield ipsilateral to the lesion. Echo suppression was abnormally weak compared with that seen in control subjects, but only for sources contralateral to the lesion. Finally, speech intelligibility tests showed normal ability to benefit from spatial separation of target and competing speech sources. These results suggest that: (1) localizing sounds within a given hemifield relies on the integrity of the contralateral IC, (2) unilateral IC lesions give the illusion that sound sources in the 'bad' hemifield are displaced towards the 'good' hemifield, (3) the IC mediates aspects of echo suppression, and (4) lesion in the IC does not impede spatial release from masking in speech intelligibility, possibly due to that ability being more heavily mediated by cortical regions.