The behavior of a sound wave is affected by the density of the medium, the temperature of the medium and the pressure of the medium if it is a gas. Motion of the medium independent of the sound wave may also affect the way sound propagates.
Yes, you may check-in for your Delta Air Lines (DL) flight with your mobile device starting 24 hours and ending 60 minutes before the scheduled departure time (depending on your departure city and destination) to receive a mobile boarding pass on your mobile device.
Delta makes exceptions for non-refundable fares in case of death of a passenger, immediate family member, or traveling companion. A death certificate must be provided to Delta to obtain the refund. To cancel your ticket on Delta Air Lines, enter your name and confirmation number and select the option to cancel. If that option isnât available, call Delta Reservations at 1-800-221-1212.