The use of mobile robots, still limited to specific applications, can be applied to service robotics such as assistance for the disabled, if efficient yet low-cost perception systems are available. A multiaural and multimodal ultrasonic device seems to be an appropriate means for achieving such a difficult compromise. In a multimodal perception system, each operating mode is suited to a specific task. The paper presents three different main working modes based on the needs of a robot for obstacle avoidance, localization and target tracking. In order to take into account either a sensor anomaly or specific constraints imposed by the robot, variations of the main modes are proposed under the name reduced service mode (RSM). Related to the main mode which is optimal a RSM establishes a new compromise between performance and response time. The paper focuses on pattern recognition -notably for target tracking- using classification by neural network but above all by statistical methods. Results show that the ultrasonic received signal allows the extraction of complex objects from the environment with a good recognition percentage. Ultrasonic technology can be used for functions different from the only obstacle avoidance.