This study describes a low bit-rate speech coding algorithm which can be applied to half-rate digital cellular and storage systems. The coding algorithm employs the temporal integration effect of the human ear that perceives short time signals as occurring concurrently. Using the result of listening tests, the length of the analysis frame and the types of excitation signals were chosen to enhance the integration effect. Informal listening tests verified that the proposed method at the rate of 4kbit/s yields better subjective quality than the 4.8kbit/s DoD-CELP(Department of Defence-CELP).