Comparison of acoustic therapies for tinnitus suppression: a preliminary trial.

OBJECTIVE: This study obtained preliminary data using two types of sound therapy to suppress tinnitus and/or reduce its functional effects: (1) Notched noise (1000-12,000 Hz notched within a 1-octave range centred around the tinnitus pitch match [PM] frequency); and (2) Matched noise (1-octave wide band of noise centred around the PM frequency). A third (Placebo) group listened to low frequency noise (250-700 Hz). DESIGN: Participants with bothersome tinnitus were randomised into one of the three groups and instructed to listen to the acoustic stimulus for 6 hours a day for 2 weeks. Stimuli were delivered using an iPod Nano, and tinnitus counselling was not performed. Outcome measures were recorded at the 0, 2 and 4 week study visits. STUDY SAMPLE: Thirty participants with constant and bothersome tinnitus were recruited and randomised. RESULTS: All groups showed, on average, overall improvement, both immediately post-treatment and 2 weeks following treatment. Outcomes varied between groups on the different measures and at the two outcome points. CONCLUSION: This study showed improvement for all of the groups, lending support to the premise that any type of sound stimulation is beneficial for relieving effects of tinnitus. These results may serve as a preliminary evidence for a larger study.

Air-leak effects on ear-canal acoustic absorbance.

OBJECTIVE: Accurate ear-canal acoustic measurements, such as wideband acoustic admittance, absorbance, and otoacoustic emissions, require that the measurement probe be tightly sealed in the ear canal. Air leaks can compromise the validity of the measurements, interfere with calibrations, and increase variability. There are no established procedures for determining the presence of air leaks or criteria for what size leak would affect the accuracy of ear-canal acoustic measurements. The purpose of this study was to determine ways to quantify the effects of air leaks and to develop objective criteria to detect their presence. DESIGN: Air leaks were simulated by modifying the foam tips that are used with the measurement probe through insertion of thin plastic tubing. To analyze the effect of air leaks, acoustic measurements were taken with both modified and unmodified foam tips in brass-tube cavities and human ear canals. Measurements were initially made in cavities to determine the range of critical leaks. Subsequently, data were collected in ears of 21 adults with normal hearing and normal middle-ear function. Four acoustic metrics were used for predicting the presence of air leaks and for quantifying these leaks: (1) low-frequency admittance phase (averaged over 0.1-0.2 kHz), (2) low-frequency absorbance, (3) the ratio of compliance volume to physical volume (CV/PV), and (4) the air-leak resonance frequency. The outcome variable in this analysis was the absorbance change (Δabsorbance), which was calculated in eight frequency bands. RESULTS: The trends were similar for both the brass cavities and the ear canals. ΔAbsorbance generally increased with air-leak size and was largest for the lower frequency bands (0.1-0.2 and 0.2-0.5 kHz). Air-leak effects were observed in frequencies up to 10 kHz, but their effects above 1 kHz were unpredictable. These high-frequency air leaks were larger in brass cavities than in ear canals. Each of the four predictor variables exhibited consistent dependence on air-leak size. Low-frequency admittance phase and CV/PV decreased, while low-frequency absorbance and the air-leak resonance frequency increased. CONCLUSION: The effect of air leaks can be significant when their equivalent diameter exceeds 0.01 in. The observed effects were greatest at low frequencies where air leaks caused absorbance to increase. Recommended criteria for detecting air leaks include the following: when the frequency range of interest extends as low as 0.1 kHz, low-frequency absorbance should be ≤0.20 and low-frequency admittance phase ≥61 degrees. For frequency ranges as low as 0.2 kHz, low-frequency absorbance should be ≤0.29 and low-frequency admittance phase ≥44 degrees.