Recorded vibrations of gray whale skulls to study how vibrations in the skull are amplified in the bony hearing complex to facilitate low frequency hearing
Data files
Apr 24, 2025 version files 6.70 MB
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amps_ALab_LACM.zip
2.29 MB
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amps_TRANSDEC.zip
2.77 MB
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drive_tables_TRANSDEC_13to15Sept2023.zip
54.48 KB
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drive_tables_TRANSDEC_19Oct2023.zip
38.12 KB
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drive_tables_TRANSDEC_28Aug2023.zip
41.61 KB
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README.md
6.07 KB
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run_descriptions_ALab_LACM.csv
2.79 KB
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run_descriptions_TRANSDEC.csv
5.41 KB
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sensor_positions.PNG
1.44 MB
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TVR_Cbass_M72.csv
52.48 KB
Abstract
Mysticete whales have a bony ear complex (tympanoperiotic complex, TPC) that supports highly sensitive hearing at low frequencies. Components of the mysticete TPC include the tympanic bulla, which is suspended from the skull by two thin, flexible bones (pedicles), and the periotic bone, which encases the cochlea and is embedded in the skull. Between the bulla and the periotic are the ossicular chain (middle ear bones) that excite the cochlear fluid and hence the sensory organs of hearing. We conducted experiments to measure the vibrational dynamics between the tympanic bullae and the base of the skull in both a juvenile and an adult gray whale. For the juvenile, assessments were performed on three versions of the skull: a plastic replica produced by 3D printing from CT scans of the original specimen, the original skull after much of the soft tissue had been removed by dissection, and the denuded skull after hydrogen peroxide was used to erode soft tissues within the cavities of the skull. We excited vibrations in the juvenile skull underwater by projecting sound in a test pool, ranging from 170 - 1000 Hz. Additionally, we measured in-air vibrations of the plastic skull, the denuded skull, and the adult skull using a mechanical shaker to drive vibrations anteroposteriorly (rostrum-to-tail) from 150 - 1000 Hz. This dataset includes recordings from 7 uniaxial accelerometers during each of the experiments. Frequency response functions (vibration velocity amplitude vs. frequency) consistently revealed amplification of vibrations at the tympanic bullae compared to the base of the skull, demonstrating a mechanism by which low-frequency sound is transferred from the environment into the inner ear.
https://doi.org/10.5061/dryad.dbrv15f90
Description of the data and file structure
run_descriptions_TRANSDEC.csv lists the run names for each in-water frequency sweep as well as descriptive data for each run including:
- local time (approx): Pacific Time at which the data was acquired
- drive table name: drive tables list the drive voltage and current for each frequency in a given sweep and are located in the folders named 'drive_tables_TRANSDEC_'
- sweep start [Hz], sweep stop [Hz], sweep step [Hz]: describes frequencies included in frequency sweep
- pulse length [ms]: duration of transmitted pulse
- pulse rate [ms]: time from the start of one pulse to the start of the next pulse
- recording length [ms]: duration of recording (recording starts on pulse-start trigger)
- skull angle [deg]: positive angles are incident on the right side of the skull, negative on the left, and 0 degrees is incident on the rostrum.
- test depth [m]: depth of skull in the TRANSDEC pool
- skull: describes the specimen used in the run
- weights & net lining: describes how much weight is where on the skull/net setup and states if there is extra lining in the net
- skull-xducer separation (pole-to-pole) [m]: approximately the distance between the transducer and the skull's center of mass
- bubble wrap position: describes where bubble wrap is placed on the skull (bubble wrap was included in some cases to block direct paths of sound from transducer to tympanic bullae)
run_descriptions_ALab_LACM.csv lists the run names for each in-water frequency sweep as well as descriptive data for each run including:
- sweep start [Hz], sweep stop [Hz], sweep step [Hz]: describes frequencies included in frequency sweep
- drive length [ms]: duration of shaker-table vibration
- recording length [ms]: duration of data recording (starts with start of vibration)
- excitation location: spot on the skull that shaker table shakes (forcing is always in the anteroposterior aka axial direction)
- skull position: describes orientation of the skull
- skull padding: describes whether the skull is on foam. one slab of foam is ~2" thick. if no foam, the skull is on solid ground.
- skull: describes the specimen used in the run
- note: in the adult skull measurements, one run includes some clipping in the data for one sensor a small range of frequencies; this is noted here.
Drive tables that list the drive voltage and current for each frequency in a given sweep listed in 'run_descriptions_TRANSDEC.csv' are grouped by date into 3 folders:
- drive_tables_TRANSDEC_28Aug2023
- drive_tables_TRANSDEC_13to15Sept2023
- drive_tables_TRANSDEC_19Oct2023
TVR_Cbass_M72.csv gives the manufacturer-provided transmit voltage response of the transducer used in the in-water experiments (TVR data was extracted from a figure in the M72-110 C-BASS datasheet: https://geospectrum.ca/wp-content/uploads/2021/04/M72-110.pdf)
Amplitude data is grouped into 2 folders:
amps_ALab_LACM: In-air experiments. Each run (as described in run_descriptions_ALab_LACM) has the following files:- 'AccelMs2_AccelData_waveform_' gives acceleration amplitude in m/s^2 at each frequency for each sensor. sensor labels are described below.
amps_TRANSDEC: In-water experiments. Each run (as described in run_descriptions_TRANSDEC) has the following files:- '
AccelMs2_RecordNI_amps_TRANSDEC_' gives acceleration amplitude in m/s^2 at each frequency for each sensor. sensor labels are described below. - '
AccelOverPressureMs2Pa_SPLfromGTI_RecordNI_amps_TRANSDEC_' gives acceleration/incident pressure in (m/s^2)/Pa at each frequency for each sensor. incident pressure is estimated using the drive voltage for each run and the manufacturer's transmit voltage response. sensor labels are described below. - '
AccelOverPressureMs2Pa_SPLfromGTI_TRANSDEC__Smooth20lowess' gives smoothed (using MATLAB's smooth(amp, 20, 'lowess') function) acceleration/incident pressure in (m/s^2)/Pa at each frequency for each sensor. incident pressure is estimated using the drive voltage for each run and the manufacturer's transmit voltage response. sensor labels are described below. (Note: there is no file in this group for run name = 28Aug2023_neg45deg_bubbleTPCR_run1)
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Sensor labels:
- TPC R (or L) axial: ASC 4221MF-002 accelerometer placed on the ventral side of the right (or left) tympanic bulla measuring in the anteroposterior direction
- TPC R (or L) transverse: PCB 333B50 accelerometer placed on the posterior apex of the right (or left) tympanic bulla measuring in the mediolateral direction
- Skull transverse: PCB 333B50 accelerometer placed on the basicranium measuring in the mediolateral direction
- Skull axial: ASC 4221MF-002 accelerometer placed on the basicranium measuring in the anteroposterior direction
- Skull normal: Dytran 3305A3 accelerometer placed on the basicranium measuring vibrations normal to the basicranium
sensor_positions.png shows accelerometer positions (a: annotated positions on plastic skull, b: sensors on natural skull, c: sensors on denuded skull, d: sensors on adult skull). Note that directions on the image are named in relation to the whale physiology: 'Mediolateral' is transverse, 'Anteroposterior' is axial, and 'Dorsoventral' is normal. 'Bulla L' = TPC L and 'Bulla R' = TPC R.
Sharing/Access information
Data was derived from the following sources:
- TVR_Cbass_M72.csv gives the manufacturer-provided transmit voltage response of the transducer used in the in-water experiments (TVR data was extracted from a figure in the M72-110 C-BASS datasheet: https://geospectrum.ca/wp-content/uploads/2021/04/M72-110.pdf
Code/Software
n/a
We conducted experiments to measure the vibrational dynamics between the tympanic bullae and the base of the skull in both a juvenile (specimen: LACM 97758) and an adult (specimen: LACM 84202) gray whale. Measurements were made by accelerometers glued with specified locations and orientations on the skull while the skull was being driven at a specific frequency, either in air or underwater. The dataset includes amplitudes of acceleration measured by 7 accelerometers positioned on the gray whale skull. Accelerometer positions are described below (begins with 'Sensor labels') and are shown in the file 'sensor_positions.jpg' (a: annotated positions on plastic skull, b: sensors on natural skull, c: sensors on denuded skull, d: sensors on adult skull. 'Plastic skull' refers to a 3D-printed replica of the juvenile skull, 'natural skull' refers to the juvenile head after most of the soft tissue was removed, 'denuded skull' refers to the skull after the rest of the soft tissue was removed by bathing the natural skull in a 12% hydrogen peroxide solution, and 'adult skull' refers to the adult skull which has no soft tissue remaining.
In-water experiments were conducted on the natural, denuded, and plastic skulls at the Naval Information Warfare Center (NIWC) Pacific's Transducer Evaluation Center (TRANSDEC) facility in San Diego, CA. Experiments were conducted using a GeoSpectrum Technologies M72-110 C-Bass transducer. Each experiment was run as a frequency sweep in the range of 170-1000 Hz, stepping through the specified frequency range at 2 Hz intervals. Each frequency was projected for 500 milliseconds at one-second intervals. Accelerometer data were recorded during each step for 700 ms, allowing the amplitude of acceleration to be calculated using a standard FFT method. This dataset includes the amplitudes of acceleration from each sensor as well as acceleration divided by incident pressure. Details of each run are described in the file 'run_descriptions_TRANSDEC.csv.'
In-air experiments were conducted on the plastic and denuded skulls in the whale acoustics lab (ALab) at UC San Diego and on the adult skull at the marine mammal collections warehouse of the Los Angeles County Museum of Natural History (LACM). Experiments in air used an Unholtz-Dickie model 5PM shaker to drive anteroposterior (rostrum-to-tail) motions in the skull at specified frequencies, and measured acceleration at the same points used in the water experiments. Employing LabView as the signal generator, the shaker vibrated for 1 s, stepping from ~150 to 1000 (or 3000) Hz in 1 (or 2) Hz intervals. At each frequency step, accelerometer data were recorded for 1 s, allowing the amplitude of acceleration to be calculated using a standard FFT method. Details of each run are described in the file 'run_descriptions_ALab_LACM.csv.' This dataset includes the amplitudes of acceleration from each sensor.
- Morris, Margaret A.; Krysl, Petr; Hildebrand, John A.; Cranford, Ted W. (2025). Experimental observation of gray whale skull vibrations amplified in the bony hearing complex. Scientific Reports. https://doi.org/10.1038/s41598-025-98100-1