System and method for eliminating audible noise for ultrasonic transducers

• US 20040202049A1
• Filed: 04/29/2004
• Published: 10/14/2004
• Est. Priority Date: 03/16/2001
• Status: Active Grant

• Current Assignee: American Vehicular Sciences LLC (Acacia Research Corporation)
• Original Assignee: Automotive Technologies International Incorporated
• Inventors: Breed, David S., Johnson, Wendell C., DuVall, Wilbur E.
• Granted Patent: US 7,079,450 B2
• Time in Patent Office: Days
• US Class Current: 367/138
• CPC Class Codes: B06B 1/0215 for generating pulses, e.g. bursts of oscillations, envelopes

Abstract

Methods for reducing clicking of ultrasonic air-coupled transducers in which a mechanical filter that attenuates audible frequencies relative to ultrasonic frequencies is placed in the path of the ultrasonic waves as the travel from the transducer to a target such as an object in the vehicle compartment.

Claims

1. A method for producing ultrasonic sound waves with an ultrasonic transducer to realize reduced audible noise, the method comprising the steps of:

arranging a filter which attenuates low frequencies to a greater extent than higher frequencies in front of the ultrasonic transducer; and

applying a transducer drive signal as input to the ultrasonic transducer to produce ultrasonic sound waves which pass through the filter and provide filtered ultrasonic sound waves with reduced audible noise effects.

2. The method of claim 1, wherein the filter is a mechanical filter.

3. The method of claim 2, further comprising the step of selecting material for the filter from an open cell plastic or rubber foam.

4. The method of claim 1, wherein the filter is an acoustic filter.

5. The method of claim 1, further comprising the steps of:

transmitting the ultrasonic sound waves from the ultrasonic transducer in a transmission path;

receiving ultrasonic sound waves reflected from a target in the transmission path;

converting the received reflected ultrasonic sound waves to an electrical signal; and

processing the converted electrical signal to obtain time and distance information related to the target.

6. The method of claim 1, wherein the ultrasonic transducer is mounted in a vehicle.

7. A method for producing ultrasonic sound waves with an ultrasonic transducer to realize reduced audible noise, the method comprising the steps of:

arranging a filter that selectively attenuates audio frequencies relative to ultrasonic frequencies in front of the ultrasonic transducer; and

applying a transducer drive signal as input to the ultrasonic transducer to produce ultrasonic sound waves which pass through the filter and provide filtered ultrasonic sound waves with reduced audible noise effects.

8. The method of claim 7, wherein the filter is a mechanical filter.

9. The method of claim 8, further comprising the step of selecting material for the filter from an open cell plastic or rubber foam.

10. The method of claim 7, wherein the filter is an acoustic filter.

11. The method of claim 7, further comprising the steps of:

transmitting the ultrasonic sound waves from the ultrasonic transducer in a transmission path;

receiving ultrasonic sound waves reflected from a target in the transmission path;

converting the received reflected ultrasonic sound waves to an electrical signal; and

processing the converted electrical signal to obtain time and distance information related to the target.

12. The method of claim 7, wherein the ultrasonic transducer is mounted in a vehicle.

13. An ultrasonic ranging system, comprising:

an ultrasonic transducer for generating ultrasonic sound waves and transmitting the ultrasonic sound waves in a transmission path, said ultrasonic transducer being arranged to receive ultrasonic sound waves reflected from a target in the transmission path and converting the received reflected sound waves to an electrical signal;

a filter for selectively filtering audible frequencies relative to ultrasonic frequencies, said filter being arranged in front of said ultrasonic transducer in the transmission path; and

a processor coupled to said ultrasonic transducer for processing the electrical signal from said ultrasonic transducer into time and distance information to the target.

14. The ultrasonic ranging system of claim 13, wherein said filter is a mechanical filter made from an open cell plastic or rubber foam.

15. The ultrasonic ranging system of claim 13, wherein said filter is made from plastic or rubber material having a density from about 1.5 to about 3 pounds per cubic foot.

16. The ultrasonic ranging system of claim 13, further comprising a housing, said ultrasonic transducer and said filter both being arranged in said housing with said filter being more proximate an opening of said housing through which the ultrasonic waves pass.

17. A vehicle including an ultrasonic ranging system, comprising:

an ultrasonic transducer for generating ultrasonic sound waves and transmitting the ultrasonic sound waves in a transmission path, said ultrasonic transducer being arranged to receive ultrasonic sound waves reflected from an object in an interior compartment of the vehicle in the transmission path and converting the received reflected sound waves to an electrical signal;

a filter for selectively filtering audible frequencies relative to ultrasonic frequencies, said filter being arranged in front of said ultrasonic transducer in the transmission path; and

a processor coupled to said ultrasonic transducer for processing the electrical signal from said ultrasonic transducer into time and distance information to the object.

18. The vehicle of claim 17, wherein said filter is a mechanical filter made from an open cell plastic or rubber foam.

19. The vehicle of claim 17, wherein said filter is made from plastic or rubber material having a density from about 1.5 to about 3 pounds per cubic foot.

20. The vehicle of claim 17, further comprising a housing recessed in a wall defining the passenger compartment, said ultrasonic transducer and said filter both being arranged in said housing with said filter being more proximate an opening of said housing through which the ultrasonic waves pass and oriented toward the passenger compartment.