Given that turning up audio volume to overcome ambient noise is a sure-fire way of ruining your hearing, is it any wonder that isolation of external sound from desired audio is a key part of headphone design?
Minutes or hours?
If using headphones for a few minutes at a time, overall comfort is probably not an issue. For longer sessions, comfort is paramount. One consideration is potential discomfort caused by the wearing of headphones on or in the ear. Custom fitting may overcome this. Ear-piece shape, padding and texture is a critical attribute of all models.
In, on or over?
It makes sense that over-ear and in-ear designs make isolation, and therefore attenuation of external noise, a simpler matter than on-ear designs. Navertheless, many folk use on-ear models and may even desire some ambient sound ingress.
Open or closed?
Open back models permit headphone audio to permeate to the outside world and vice versa. Whilst open backs may enhance frequency response characteristics, many find the sound leakage annoying. Closed back models tend to keep the inside sound in and the outside sound out.
What's the frequency response?
The frequency range of human hearing is commonly given as 20 to 20,000 Hz (Wikipedia). For a given signal amplitude, headphones should ideally translate all frequencies in that range to sound waves of equal loudness, a 'flat' response curve. Tone equalisation controls exist to compensate where headphones, and listeners' ears, are less than ideal.
And the choice is?
Headphone choice is highly subjective. In my view, over-ear designs are better for comfort and attenuation of external noise. I like my old AKG K55's (light, comfortable, closed-back, high ambient noise attenuation). The 2016 AKG trio of K52, K72 & K92 has the desired qualities and is arguably more stylish.
K52, 18Hz-20kHz frequency range, all-black styling.
K72, 16Hz-20kHz, longer 3-metre cable + screw-on 1/4" adapter, black & silver styling.
K92, 16Hz-22kHz, gold-plated adapter, black & gold styling.