Ludwig Desire Johan Eggermont

Some design issues in digital signal processing for digital-audio systems

Considerations leading to the introduction of the concept of an integrated digital-audio system are presented. Emphasis is placed on its relation to different application areas of digital signal processing. In digital-audio systems some signal processing algorithms can be applied which are unique in the sense that they are related to the acoustic environment. The resulting large signal delays pose problems in the analysis of finite wordlength and overflow effects. For one of the constituing filters of a digital reverberator a design solution is obtained both by calculation and simulation. Some subjective effects are demonstrated at the paper presentation.

Signal/Quantizing-distortion ratio measurements of fast-adaptive delta modulation systems

Signal/quantizing-distortion ratio (SQDR) was measured as a function of input level at a sampling frequency of 64 kHz with a phase- and amplitude-modulated sine wave of 800 Hz as input signal for different adaptive delta modulation systems. The parameters are: the number of bits taken into account in deciding step-size changes (bit-memory length); the ratio between the number of successive identical bit repetitions after which the step size is increased and the number of consecutive bit alternations after which the step size is decreased (up/down ratio); the step-size change factor a; and the use of single or double integration. Only one parameter is changed at a time resulting in a total of 54 measurement curves of SQDR as a function of input level. An analysis of the measurements is presented in terms of an averaged SQDR and its systematic spread as a function of the parameters.