More important than the ability to block noise is the ability to create it, and this is something that the ANC9s do very well, especially when noise cancellation is active. In effect, switching them on sounds like adding a loudness boost on an MP3 player. The audio across all frequencies lifts; high-range sound really snaps and the bass rumbles. But it's the mid-range sounds that had us grinning. Often the mids are the first casualty of inferior headphones, where the intricacies of the sound are lost behind thumping kick drums and bass. With the ANC9s, we can hear lots of detail in the sound.
Without power, the headphones still work in a passive capacity, though you do lose some of that clarity we just described. The sound is still good, but without power, the sound definitely favours the lower frequencies.
The ANC9s provide a comfortable fit, even for long stretches of time. Audio Technica uses memory foam in the cups and along the headband, which does heat up a little bit, but never enough to be uncomfortable. The cup covers are easily removed, in case you want to give them a wipe down or replace them.
The Audio-Technica ATH-ANC9s are a great-sounding pair of noise-cancelling headphones, but you'll have to keep a packet of AAA batteries handy if you want to get the most out of them. This will gall some music lovers, especially when Audio-Technica is asking AU$349 for them. The sales package is rather generous, though, with a tough-shell case, an alternative hands-free cable with a microphone and a two-prong aeroplane adapter; but a rechargeable battery would definitely have been the icing on the cake.