As automotive audio market calls for higher loudspeaker performances and shorter time-to-market, there is a need for improved loudspeaker design techniques. Here, an innovative synthesis approach is proposed. First, the non-linear characteristic of each loudspeaker component (spider, cone, and magnetic circuit) has been individually either measured or simulated using a FEA software. Then, given technical specifications, the data pertinent to each component is used to simulate the performance of the loudspeaker. This way, any solution can be explored at synthesis level before prototype assembly, and components can be chosen to guarantee the best fit to customer specifications. Comparison between simulated and measured data is presented to validate the model.
Convention Paper 5539

14:30 h
H2 Effects of Background Noise on the Perceived Quality of Car Audio Systems – Emanuele Ugolotti¹, Enrico Armelloni², Fabio Bozzoli², Angelo Farina² - ¹ASK Automotive Industries, Reggio Emilia, Italy; ²University of Parma, Parma, Italy

The paper describes the recording/reproduction technique and the subjective listening experiment aimed to the assessment of the effect of the background nose on the perceived quality of the sound being reproduced inside a car. The noise inside 4 different cars was recorded at various speeds both with a binaural microphone and with a Soundfield microphone. These background noise recordings are reproduced inside a special listening room, by means of a very sophisticated reproduction chain, designed so that at the ears of the listeners the same sound pressure is presented as inside the original car. A computer-based system is finally employed for collecting subjective responses to sound stimuli, constituted by the reproduction of music or speech on an automotive sound system in presence of the background noise.
Convention Paper 5540

15:00 h
H3 Different Approaches for the Equalization of Automotive Sound Systems – Angelo Farina¹, Alberto Bellini¹, Marco Romagnoli² - ¹University of Parma, Parma, Italy; ²ASK Automotive Industries, Reggio Emilia, Italy

The paper discusses various possible DSP algorithms employable on low-cost platform suitable for mass series production of automotive sound systems. The analysis takes into account traditional IIR and FIR filtering schemes, dual-rate and hybrid approaches, and new algorithms such as Warped FIR (WFIR) or frequency-domain partitioned convolution (BruteFIR). The comparison does not limits to the implementation, cost and performance of different processing schemes, but also to the hot problem of computing the optimal filtering coefficients for each of these schemes starting from measurements taken inside the car cockpit, making use of examples taken from the real life. The results show that both IIR and FIR structures are capable of good results on low-cost DSP systems; the more advanced algorithms will probably become competitive as soon as a new generation of floating-point DSP processors will also be available for low-cost applications.
Convention Paper 5541

15:30 h
H4 Design of a Digital Audio Equalizer for Automotive Applications – Alberto Bellini, University of Parma, Parma, Italy; Monica Tesauri¹, Emanuele Ugolotti¹, Eraldo Carpanoni², Giacomo Frassi² - ¹ASK Automotive Industries, Reggio Emilia, Italy; ²University of Parma, Parma, Italy

The project deals with the design and realization of a dedicated board for the processing of audio signals for automotive applications, named DIGIcar. It features two stereo inputs (24 bit resolution) and two stereo outputs. The prototype was realized in a 4 layer PCB with SMD components. The DIGIcar board was tested stand-alone with an Audio Precision System 2022. Experiments were performed inside a car too, where the DIGIcar board was interfaced with a four channel power amplifier and connected between audio source and car loudspeakers. A development tool in MATLAB was exploited in order to synthesize the suitable equalizing filters, given standard acoustic car measurements. Then the filters are stored in the board FLASH EEPROM. A few options are available to tailor the equalizer for different cars. Listening tests and acoustic measurements show the effectiveness and the functionality of the designed board.
Convention Paper 5542

16:00 h
H5 Single-Channel Noise Reduction for Hands-Free Operation in Automotive Environments – Stefan Schmitt, Malte Sandrock, DSPecialists GmbH, Berlin, Germany

The objective of this work is to establish a single channel noise reduction algorithm for speech enhancement integrated in DSP systems. The main emphasis is on spectral subtraction. The chosen algorithm is based on a Minimum Mean Square Error Log Spectral Amplitude (MMSE-LSA) approach. One of the crucial tasks for good results, i.e. natural and intelligible speech in combination with well attenuated noise and low spectral distortion, is a balanced estimation and weighting of the noise magnitude spectrum.
Convention Paper 5543

16:30 h
H6 Active Design of Automotive Engine Sound - Rolf Schirmacher, Müller-BBM GmbH, Planegg, Germany

For many years, active noise control (ANC) is a concept strongly discussed for the reduction of unwanted sounds. In addition to minimizing noise, this technique can be extended to achieve a target sound which is different from silence. This concept is called Active Sound Design (ASD). It does not only reproduce a target sound, but monitors the sound and uses a closed control loop . This results in a high quality reproduction and allows the target sound level to be lower or higher than the original sound level without system. One major application is the automotive engine noise. ASD allows to merely freely define the engine sound independent of the physical engine used in the car. The paper presents the concept of ASD and reports on applications of this technique for automotive interior and exterior sound.
Convention Paper 5544