Impulsive Knocks Recorded Underwater in Glacier Bay

Notes on Sound Clips
The recordings below were made by the National Park Service, using a hydrophone that is anchored near the mouth of Glacier Bay, Alaska for the purpose of monitoring ambient noise. The recordings are intended to provide examples of the types of natural and manmade sounds that occur in Glacier Bay National Park.

Impulsive Knocks Recorded in Glacier Bay

Recorded in 2022-2023, the following sounds are believed to be from humpback whales.

 

Single, Double, and Triple Impulsive Knocks

These sounds are examples of three different types of impulsive knocks observed on recordings from remote cabled hydrophone in Glacier Bay, Alaska. Researchers believe these are made by humpback whales. On average, impulsive knocks have a mean peak frequency of 1.1 kHz are 0.128 sec duration, and occupy the entire 20 Hz – 21.9 kHz band. In the case of double and triple pulse knocks, the pulses occur 0.267 sec apart on average.

 

Single, Double, and Triple Impulsive knocks recorded on spectrograms showing frequency (1 - 22 kilohertz) on the vertical axis and time on the horizontal axis.

NPS / C. Gabriele

 

• Single Impulsive Knock

  
  

  Single pulse knock recorded September 19, 2022, 23:41:50 amplified by 6 decibels

  Credit / Author:

  NPS / C. Gabriele

  Audio Transcript

  Sounds of swishing water, followed by a single crack or popping sound.

 

• Double Impulsive Knock

  
  

  Double pulse recorded May 15, 2023, 13:36:16, amplified by 6 decibels.

  Credit / Author:

  NPS / C. Gabriele

  Audio Transcript

  Sounds of swishing water. Two successive cracks, or pops, follow each other in quick succession.

 

• Triple Impulsive Knock

  
  

  Triple pulse recorded September 20, 2022 05:35:28 amplified by 6 decibels.

  Credit / Author:

  NPS / C. Gabriele

  Audio Transcript

  Sounds of water in the background, then three successive knocking sounds in quick repetition.

 

Call and Response Knocks?

 

One or two animals making impulsive knocks sounds together. Sound spectrogram shows frequency (1 - 11 kilohertz) on the vertical axis and time on the horizontal axis.

NPS / C. Gabriele

 

• Two or More Animals Impulsive Knocks

  
  

  A 45-second recording of two or more animals making impulsive knocks, denoted A and B, on April 19, 2017 at 09:48:41. Researchers think these are sounds made by humpback whales.

  Credit / Author:

  NPS / C. Gabriele

  Audio Transcript

  A series of cracks or snapping sounds likely created by one or two humpback whales. The faint high pitched whines or vocalizations of humpback whales can be heard accompanying the loud cracks.

 

Field Recording of Loud Snaps Made by a Humpback Whale

 

Sound spectrogram showing frequency (1 - 24 kilohertz) on the vertical axis and time on the horizontal axis. Recorded on a hydrophone (underwater microphone) near Bartlett Cove, Glacier Bay National Park.

NPS / C. Gabriele

 

• Loud Impulsive Snaps

  
  

  Loud impulsive “snaps” recorded while male humpback whale (ID #1065) was observed chasing female (#1019) within 300 m of research vessel in Icy Strait, Alaska, September 29, 2009. Social sounds and song audible (and visible) in background. This recording demonstrates that humpback whales produce loud broadband pulses in Alaska.

  Credit / Author:

  NPS / C. Gabriele

  Audio Transcript

  Swishing sounds of water, four loud snaps or cracking sounds, accompanied by faint sounds of humpback whales vocalizing.