DOI: 10.5061/dryad.dbrv15f90
title: 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

description: 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. 
description: 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.
description: # 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
 [https://doi.org/10.5061/dryad.dbrv15f90](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](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) 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](https://geospectrum.ca/wp-content/uploads/2021/04/M72-110.pdf) ## Code/Software n/a