DOI: 10.5061/dryad.f4qrfj759
title: Temporary threshold shifts from mid-frequency airborne noise exposures in seals

description: To evaluate the residual effects of airborne noise, hearing thresholds
 were obtained before and after noise exposure using behavioral
 psychophysics for two phocid carnivores: a northern elephant seal
 (Mirounga angustirostris) and a harbor seal (Phoca vitulina). The seals
 were trained to position calmly during exposure to octave-band white noise
 centered at 1 or 2.5 kHz with varying level (65 to 125 dB sensation level,
 SL) and duration (1.5 to 50 min). Threshold shifts were determined at the
 center frequency of the noise band as the difference between detection
 thresholds measured prior to and following noise exposure. Results
 indicated that (1) neither seal exhibited consistent recoverable hearing
 loss (temporary threshold shift, TTS) to noise levels &lt; 85 dB SL or
 durations below 12 min; (2) an equal-energy relationship between noise
 level and duration did not predict observed patterns of TTS; and (3) the
 harbor seal demonstrated two distinct responses to noise, with the sound
 exposure level required to induce TTS increasing by 24 dB in a second
 experimental phase. Phocids appear less susceptible to hearing loss from
 airborne noise exposures than otariid carnivores, apparently due to
 attenuation through permanent or active closure of the meatus during
 exposure to high-noise conditions.
description: # Temporary threshold shifts from mid-frequency airborne noise exposures
 in seals Dataset DOI: [10.5061/dryad.f4qrfj759](10.5061/dryad.f4qrfj759)
 ## Description of the data and file structure To evaluate the residual
 effects of airborne noise on pinnipeds, hearing thresholds were obtained
 for two seal subjects before and after exposure to mid-frequency,
 octave-band noise in an acoustic chamber. Behavioral psychophysical
 methods were used to cooperatively evaluate hearing. Temporary threshold
 shift (TTS) was measured as the difference between a seal's
 pre-exposure hearing threshold and the subsequent post-exposure hearing
 threshold at the center frequency of the noise band.   The datasets
 included here comprise raw hearing thresholds and TTS measurements for all
 noise level/duration conditions, supplementary heart rate measurements for
 the harbor seal subject, and supplementary video data of the harbor seal
 subject's meatal opening during testing. Additional details are
 provided in the associated manuscript text.  ### Files and variables ####
 File: raw_TTS_data.xlsx **Description:** Raw data are presented for each
 noise exposure and control sequence conducted throughout this study. These
 data support the presentation of summarized data in Figures 1 and 2 and
 Table II of the primary manuscript. ##### Variables * Subject: *Phoca*
 (harbor seal) or *Mirounga* (northern elephant seal) * Phase: Phase 1 or 2
 of TTS testing * Date: YYYY MM DD of test sequence * Frequency (kHz):
 center frequency of the octave-band noise exposure * Noise Level (dB SPL):
 noise exposure level in absolute terms (unweighted sound pressure level,
 dB re 20 μPa); this is entered as "n/a" (not applicable) for
 control (no-noise) sessions * Noise Level (dB SL): noise exposure level
 defined relative to sensation level (SL, dB re hearing threshold); this is
 entered as "control" for no-noise sessions * Noise Duration
 (min): duration of noise exposure or control (no-noise) condition * Noise
 Exposure Level (dB SEL): noise exposure level expressed as unweighted
 sound exposure level (SEL, dB re (20 μPa)^2 s); this is entered as
 "n/a" (not applicable) for control (no-noise) sessions *
 Baseline threshold (dB re 20 μPa): hearing threshold obtained just prior
 to noise exposure * Exposure threshold (dB re 20 μPa): hearing threshold
 obtained immediately following noise exposure * Recovery threshold (dB re
 20 μPa): hearing threshold obtained 24 h following noise exposure *
 Threshold Shift (dB): difference between exposure threshold and baseline
 threshold #### File:
 supplementary_HR_raw_data_associated_with_footnote_2.xlsx
 **Description:** Complementary physiological data were obtained for the
 harbor seal subject (*Phoca*) during Phase 1 of this hearing study. The
 seal was conditioned to wear a Polar S710 heart rate monitor (Polar
 Electro Inc., Woodbury, New York, USA) on an elastic band voluntarily
 secured around his axillary girth. This provided a continuous ECG record
 from which mean heart rate could be extracted for many of the exposure
 sessions shown in Table I of the manuscript. The heart rate data were
 highly reliable. While we had hypothesized that heart rate during the
 exposure interval would differ based on noise exposure conditions, we
 found no apparent difference in overall heart rate in control versus noise
 exposure sessions, no difference with increasing exposure duration, no
 difference with increasing sound pressure level, and no difference in
 exposure sessions resulting in measurable TTS. This indicates that
 auditory effects of noise exposure can occur in cooperative subjects in
 the absence of physiological markers of stress. This observation is
 reported as a personal communication by one of the authors (C.
 Reichmuth). Raw heart rate data for this subject are available in the
 supplementary data file.   ##### Variables * Subject: *Phoca* (harbor
 seal) * Phase: Phase 1of TTS testing * Noise Level (dB SL): noise exposure
 level defined relative to sensation level (SL, dB re hearing threshold) *
 Noise Duration (min): duration of noise exposure or control (no-noise)
 condition * HR mean bpm: average heart rate (beats per minute)  * HR min
 bpm: minimum heart rate (beats per minute) * HR max bpm: maximum heart
 rate (beats per minute) * St Dev: standard deviation of heart rate data  *
 mean TTS: average temporary threshold shift for a level/duration condition
 #### File: supplementary_HR_summary_data_associated_with_footnote_2.xlsx
 **Description:** Complementary physiological data were obtained for the
 harbor seal subject (*Phoca*) during Phase 1 of this hearing study. The
 seal was conditioned to wear a Polar S710 heart rate monitor (Polar
 Electro Inc., Woodbury, New York, USA) on an elastic band voluntarily
 secured around his axillary girth. This provided a continuous ECG record
 from which mean heart rate could be extracted for many of the exposure
 sessions shown in Table I of the manuscript. The heart rate data were
 highly reliable. While we had hypothesized that heart rate during the
 exposure interval would differ based on noise exposure conditions, we
 found no apparent difference in overall heart rate in control versus noise
 exposure sessions, no difference with increasing exposure duration, no
 difference with increasing sound pressure level, and no difference in
 exposure sessions resulting in measurable TTS. This indicates that
 auditory effects of noise exposure can occur in cooperative subjects in
 the absence of physiological markers of stress. This observation is
 reported as a personal communication by one of the authors (C.
 Reichmuth). Summary heart rate data (by noise condition) for this harbor
 seal subject are available in the supplementary data file. Heart rate (HR)
 data are given as the mean, min, max, and std dev of the sessions for
 which HR data were obtained (n sessions). TTS data are averages for the
 same level/duration conditions presented in the corresponding paper. Cells
 filled with "n/a" indicate that data are not available. These
 are the summary data for the raw data provided in
 supplementary_HR_raw_data_associated_with_footnote_2.xlsx.   #####
 Variables * Noise Duration (min): duration of noise exposure or control
 (no-noise) condition * Noise Level (dB SL): noise exposure level defined
 relative to sensation level (SL, dB re hearing threshold) * sessions (n):
 number of sessions for which heart rate data were obtained * mean HR:
 average heart rate (bpm, beats per minute)  * min HR: minimum heart rate
 (bpm, beats per minute) * max HR: maximum heart rate (bpm, beats per
 minute) * St Dev HR: standard deviation of heart rate data  * mean TTS:
 average temporary threshold shift for a level/duration condition ####
 File: supplementary_video_footage_associated_with_footnote_3.mp4
 **Description:** Video footage showing the protective mechanism observed
 at the right external ear during voluntary noise exposure in a harbor
 seal. Clips 1, 3, 4, 5, 10, 11, 13 and 16 were obtained in the presence of
 fatiguing noise. Clips 2, 6, 7, 8, 9, 12, 14, and 15 were obtained during
 subsequent auditory testing with near-threshold-level stimuli. Footage
 obtained 12 November 2004.