Due to this high prevalence, vertebral artery hypoplasia (VAH) has not yet been considered an independent risk factor for ischemic stroke [1,2].
How to use your own headphones on Americanâs new 777-300ER. Passengers traveling in First and Business Class on Americanâs new 777-300ER are provided with Bose QuietComfort 15 Acoustic Noise Canceling headphones to use during the flight.
They are designed specifically to block constant, low frequency noises, and are excellent for planes trains and automobiles. Noise cancelling headphones provide approximately -15dB ~22dB of isolation, mainly in the lower frequencies.