Directional Sound Speaker

Key Role and Technical Requirements of Ultrasonic Sensors in Directional Sound Systems

1. As a Transmitter: Constructing a Directional Sound Beam

   • Single Sensor Emission:
     A single ultrasonic sensor emits a narrow-beam ultrasonic wave, directly covering the target area. For example, small directional sound systems (like guides) use a single transducer for close-range sound transmission.

   • Multi-Sensor Array (Phased Array Technology):

     • Beam Direction Control: Multiple ultrasonic sensors are arranged in specific arrays (e.g., linear, planar). By adjusting the phase difference of each sensor's emission, the direction of the combined sound beam is altered (similar to radar phased array scanning).

     • Focusing and Diffusing Control: Adjusting the amplitude and phase of the array can focus the sound beam to a distant point or diffuse it to cover a specific area (e.g., a fan-shaped region).

     • Application Example: In large public spaces (e.g., museums, exhibition halls), directional audio systems use sensor arrays to accurately direct sound to different exhibit areas.

2. As a Receiver: Environmental Sensing and Feedback Adjustment

   • Echolocation:
     After emitting a signal, the ultrasonic sensor receives reflected echoes from the environment for:

     • Obstacle Detection: Identifies obstacles (e.g., walls, crowds) to prevent beam obstruction or interference from reflections.

     • Distance Measurement: Measures the distance to the target area, dynamically adjusting emission power or beam angle (e.g., in car-based directional sound systems adjusting beam focus based on vehicle distance).

   • Adaptive Sound Field Optimization:
     Using feedback from the receiver (e.g., sound pressure level, interference frequency), emission parameters (such as frequency or phase) are adjusted in real-time to suppress environmental noise or echo reflections, enhancing sound quality.

Advantages:

1. High Directionality:
   The ultrasonic beam width can be as narrow as a few degrees (e.g., 5°–15°), compared to traditional sound systems with dispersion angles >60°. This concentrates sound energy in the target area, minimizing interference with surrounding areas (e.g., store guides in malls not disturbing other shops).

2. High Privacy:
   The sound pressure outside the beam is very low (typically <30 dB), making it almost inaudible. This is ideal for private audio transmission in sensitive environments (e.g., hospitals, libraries).

3. Long-Distance Transmission:
   While high-frequency ultrasonic waves attenuate quickly in air, focusing technology through arrays allows for directional sound propagation over distances of tens of meters (e.g., plaza announcements, airport runway guidance).