In a low bit-rate audio transform coding system, the quantization noise is spread out over the entire analysis block in the time domain after the inverse transformation in the decoder. This increases the likelihood of pre-echoes occurring prior to a transient event. In order to control preechoes level, a suitable quantizer should be applied in the coder. This paper presents such an optimum quantizer design by a study of the input signal characteristic in terms of its dynamic range and probability density function (PDF) and a comparison study of different quantizers in a low constant bit rate audio coder with adaptive window switching technique. The performance of quantizers is measured by an objective mean i.e. the average segmental signal-to-noise ratio (SEGSNR).The Laplacian quantizer provides excellent results for the quantization of the transient signal with an increase of about 9 dB in the SEGSNR as compared to the non-uniform quantizers(MPEG-4).