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.
Within 24 hours of your departure, you can tell us how many bags you will check and pay any fees quickly and easily online. That means one less thing you will have to do at the airport. When you arrive at the airport, you can drop off your checked baggage at the nearest baggage drop, marked with red Baggage Drop signage, or curbside check-in station (available within 6 hours of departure time). You may also check your bags at the airport kiosk, ticket counter, or curbside. https://www.delta.com/content/www/en...aggage_Ongoing