Khun ดาวเหนือ, most of the better sound and famous headphones are open type, ie you WILL hear the sound from the outside while you wear it. In a way, it seems even 'LOUDER' than when you don't wear the headphone. It's just my thinking that the structure of these open type headphone makes it louder. The famous open type includes Grado SR-60 and SR-125, and Sennheiser HD 580, 600 and 650. Senn's impedance is 300 ohm krub.
As such, you will need some isolation if you don't want any interruption. These headphone are sealed type and in-ear type.
As far as I know of, a typical sealed headphone is not popular for good sound quality and is unlikely to be comfortable, particularly in the relatively humid and warm weather
Thailand.
The in-ear canal type seems to be a good candidate. It kinda blocks out the sound from the environment so you could use it while travelling on public transportation
bus and train. The entry level one is from Sony EX series. The ones that sounds good come from Shure, Etymotic and Ultimate Ears. The one that is famous is more expensive than the famous open type above. Cheapest famous one is Shure E3 which retails at US$170 in the US (around Bt7,000 in Thailand).
Khun Poj uses this earphone and you can find his comment here.
http://www.thaiavclub.org/forum/index.php?showtopic=2844&st=0&#entry28170Nevertheless, both sealed and in-ear type will not protect the sound if someone PULLs your headphone out and yell into your ear as they talked to you and there is no response though.
