Fig 1. A screen shot from a towed PAM system showing seismic pulses and dolphin click/whistles. Vertical scale is 10-22000Hz, horizontal scale is time with approximately 10 seconds between seismic pulses and colour coding is signal intensity.
This is one of the key concerns raised by environmental groups (eNGOs) and some regulators. In fact, eNGOs often make comments such as “Noise from …… seismic work ….. can make it difficult for these very social animals to communicate with one another” in their blogs or media releases. Note the judicious use of the word “can” when there is no evidence that cetacean communication is prevented by seismic sounds but significant evidence to the contrary. After all, it is the eNGOs and many regulators who insist on the use of passive acoustic monitoring (PAM) techniques during seismic surveys to detect the location of vocalizing whales and dolphins. If one were to consider a PAM recorder (or hydrophone) as a cetacean ear then surely if the PAM recorder can differentiate between the sounds emitted by a variety of species of cetaceans in the presence of seismic sounds then there should be no issues with communicating. The following displays provide evidence that dolphins, sperm whales and blue whales continue to vocalise during seismic surveys and their vocalisations (or “languages”) can easily be recognized by computer software and humans. However even though we do not know what their vocalisations mean, other individuals of the same species will obviously know, thereby enabling them to communicate.
Displays such as those shown above demonstrate that cetaceans continue to vocalise clearly and at similar intensities to seismic sounds during seismic surveys. The fact that cetaceans successfully live in noisy environments for significant lengths of the year can also be found in Antarctic waters where the sounds of calving/cracking/colliding icebergs are as intense as and at similar frequencies to seismic sounds.
Thus, it is inconceivable that seismic sounds prevent cetaceans from communicating.