[LAD] incorrect number of samples reading from /dev/dsp1

Hi All, I am trying to read data from a usb microphone and using the pretty standard method of using ioctl's to setup the sampling rate, channels, bits and block size . This all works so the device is correctly setup. I then use "read" to read samples from the device which shows up as /dev/dsp1. I get a lot more samples from this read command in one second of recording than the set sample rate. E.g. if i set 10Khz on one run i got 269312 samples. Looking at the raw data it looks like there is a lot of duplication of data? is this common for the audio input device? if so what kind of encoding is it (e.g with some specific redundancy built in)? thanks farhan