It's generally the case that good-quality earphones should be top of your shopping list after buying a decent portable music player, as the supplied ones are rarely up to scratch.

But it's important to consider the impact of background noise on the listening experience too. Given the noisy places such devices are used – gyms, public transport, city centres – it's all too tempting to crank up the volume to potentially harmful levels. Noise-isolating earphones are a safer answer to the problem.

Not to be confused with more expensive noise-cancelling earphones, which use special circuitry to remove external cacophony, the CX400s' soft rubber attachments are supposed to do much the same job.
When you place the CX400s in your ears there's a sudden silence akin to wearing a pair of earplugs, because they fill the ear canal entirely, creating a seal (don't worry, it's not painful).

Start the music, though, and the silence is replaced by rich, powerful bass and crisp higher frequencies with no distortion when turned up loud. Sound quality could almost be compared to that of full-size studio headphones. Besides the near complete absence of external noise, the next thing you will notice is that they require a much lower volume setting than a conventional set of earphones.

The CX400s are closed-back earphones, which means that sound cannot escape from the earphone housing – useful for listening to music in a quiet environment without disturbing others. The Sennheiser CX400s have all the hallmarks of a premium audio product, which justifies the relatively high price tag.

We were pleased to find three separate pairs of rubber attachments in the pack to cater for all ear sizes, making for a snug, comfortable fit. There's also a smart leather pouch in which to store everything. The only weakness we found was that whenever the cable was snagged – on a jacket zip, for example, there was an audible thud.

However we were able to prevent this to some extent by using the supplied clip, which makes the CX400s a good recommended for urban commuters and for anyone who cares for their ears.