Temporary threshold shifts from mid-frequency airborne noise exposures in seals
Data files
Jul 30, 2025 version files 433.08 MB
Abstract
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 < 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.
Dataset DOI: 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.