In November 2002, scientists recorded calls in the presence of sei whales off Maui. All the calls were downswept tonal calls, all but two ranging from a mean high frequency of 39.1 Hz down to 21 Hz of 1.3 second duration – the two higher frequency downswept calls ranged from an average of 100.3 Hz to 44.6 Hz over 1 second of duration. These calls closely resembled and coincided with a peak in "20- to 35-Hz irregular repetition interval" downswept pulses described from seafloor recordings off Oahu, which had previously been attributed to fin whales. Between 2005 and 2007, low frequency downswept vocalizations were recorded in the Great South Channel, east of Cape Cod, Massachusetts, which were only significantly associated with the presence of sei whales. These calls averaged 82.3 Hz down to 34 Hz over about 1.4 seconds in duration. This call has also been reported from recordings in the Gulf of Maine, New England shelf waters, the mid-Atlantic Bight, and in Davis Strait. It likely functions as a contact call.