I have got a sony Nw hd5 player; on cnet, it is reported to have a very good signal-to-noise ratio, as they say (around 95dB). But one can clearly hear the disk spinnig up occasionally (on quiet songs), not to mention some other faint sounds, with any decent headphone. Is it normal? and has any one got a link to a review comparing players'sound quality which would include the nw hd5?

Yes, I hear the disk spinning too. And the faint sounds are very much there when you're listening at night with the volume at absolute minimum.

Low volume listening can be annoying...

Maybe I misunderstand you, but hearing the disk spinning, or any mechanical sound what-so-ever, has nothing to do with signal to noise ratio. This is a measure that applies only to the electrical signal coming out. You hear the result in the headphones but any other noises you hear that are not part of the audio signal are irrelevant to this metric.

Sorry, I wasn't clear enough; I mean I can actually hear noise through the headphones (although occasionally). Is it normal ?

That is not normal.

The device does not really have a practical 95dB *SNR if you can hear the disk in the signal. If it's really 95dB SNR, you will not hear anything except for the files you play. There is a chance that the measurement used was done in a period where the disk was not spinning(music was loaded to internal buffer). But it is still not an accurate measurement if you can hear the disk spin. For this device, you need to spec multiple SNRs depending on what it is doing. From what you describe, this thing is a poorly designed device and you should return it and try another one, or just return it and buy another product if that is possible.

*SNR measurements should always be made at multiple volume positions. If a device uses a DSP volume control, the SNR may alter substantially at different volume levels. On a device with such a DSP volume control, the 100% volume SNR measurement may not be applicable if you are using 70% volume, for example.

-Chris