Patent Publication Number: US-6668204-B2

Title: Biaural (2channel listening device that is equalized in-stu to compensate for differences between left and right earphone transducers and the ears themselves

Description:
The instant application claims priority to U.S. Provisional Application, Ser. No. 60/237,641, filed Oct. 3, 2000, which is herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The invention generally relates to an audio headphone or hearing aid device and, more particularly, to a headphone or hearing aid device that allows for compensation of imperfections in the listener&#39;s hearing. 
     (2) Description of Prior Art 
     The most popular current means of personal on-demand audio entertainment is delivered by means of headphones connected to a source device by wires. The sound source may be portable as in the typical Walkman (registered trade name) device shown in FIG.  1 . Here the audio content is stored in magnetic, optical or solid state media (not shown) housed within the player  10 . The signals from these media are converted to audio signals that are amplified prior to delivery by wires  12  to transducers within headphones or earphones  14 . Other sound sources may not be portable such as typical home stereo systems. 
     Hearing-impaired persons are fitted with hearing aids, sometimes in both ears. Transducers for both headphones and hearing aids are typically electro-mechanical devices that cannot be matched during manufacturing within reasonable costs. The auditory responses of both left and right ears are not perfectly matched; however, current headphone devices assume that they are. With imperfections of both the transducers and the ears, the auditory perception of the position of the audio source may be shifted from the original location. If measurements are made of the ear responses and correctional hearing aids manufactured, proper correction may not be achieved due to imprecise matching of transducers. 
     Several methods have been devised for improvement of hearing aid devices. U.S. Pat. No. 6,104,822 to Melanson et al. describes a hearing aid device with multiple user selectable digital signal processing methods for improving hearing under different listening environments. U.S. Pat. No. 6,128,392 and European Patent 0 933 970 A2 to Leysieffer et al. describe a hearing aid device using finite impulse response filtering to achieve feedback compensation. Hanson (European Patent 0 634 084 B1) describes a hearing aid feedback compensation device where adaption rates vary depending upon signal conditions. U.S. Pat. No. 5,500,902 to Stockham, Jr. et al. describes a hearing aid device with a plurality of bandpass filters each with a corresponding automatic gain control. This allows volume compensation over different frequency ranges. U.S. Pat. No. 6,072,885 also to Stockham, Jr. et al. expands the previous invention by providing separate low and high frequency output transducers. 
     Improvements have also been made in the spatial perception experience for audio listeners. U.S. Pat. No. 5,136,651 to Cooper et al. describes an audio system whereby compensation for head diffraction is accomplished. U.S. Pat. No. 5,939,656 to Suda describes an audio system that compensates for the differences in frequency and sound image location between speakers and headphones. U.S. Pat. No. 6,005,947 to Lim describes an acoustic processing system that mimics the quality of an acoustically ideal listening room. U.S. Pat. No. 6,111,958 to Maher describes an audio processing system that improves the spatial imaging of signals. 
     The wires often used in headphone systems can impede motion of the user and are prone to failure due to handling. Several methods have been devised to eliminate this problem. One such method is U.S. Pat. No. 5,247,293 to Nakagawa shown in FIG. 2 where the player  10  and headphones  14  are separated. The two units are coupled by radio frequency signals allowing transmission of the audio signal to a smaller, less cumbersome, remote unit  18 . The headphones  14  still use wires  12 . The remote unit  18  allows control of the player  10  functions such as volume, fast forward, etc. Vertical Horizon markets a headphone unit (Korea patent pending number 99-24278) that allows downloading of 32 Mbytes of MP3 audio content from a computer parallel port. In this case, the storage and controls are all contained within the headphone unit. Downloading is accomplished through a wired connection. Sennheiser markets a wireless listening system where a transmitter unit is connected to an audio source. This is coupled via a 900 MHz radio frequency signal to a pair of headphones. 
     SUMMARY OF THE INVENTION 
     A principal object of the present invention is to provide an audio headphone device having an interactive process whereby compensation for imperfections in the hearing of the user may be accomplished. 
     A second object of the present invention is to provide an audio headphone device having an interactive process where compensation for imperfections in the hearing of the user may be accomplished and where correction information may be stored within the headphone device. 
     Another object of the present invention is to provide an audio headphone device having an interactive process where compensation for imperfections in the hearing of the user may be accomplished and where correction information may be stored within the sound source. 
     Another object of the present invention is to provide an audio headphone device having an interactive process where compensation for imperfections in the hearing of the user may be accomplished and where correction information may be stored within a personal computer. 
     Another object of the present invention is to provide an audio headphone device having an interactive process provided by a personal computer or other sound source whereby compensation for imperfections in the hearing of the user may be accomplished. 
     A still further object of the present invention is to provide an audio headphone device having an interactive process whereby compensation for imperfections in the hearing of the user may be accomplished where connection to the sound source is achieved using wireless means such as infrared, radio frequency or electromagnetic means. 
     A still further object of the present invention is to provide a hearing aid device having an interactive process whereby compensation for imperfections in the hearing of the user may be accomplished. 
     A yet further object of the present invention is to provide a hearing aid device having an interactive process where compensation for imperfections in the hearing of the user may be accomplished and where correction information may be stored within the hearing aid device. 
     Another object of the present invention is to provide a hearing aid device having an interactive process provided by a personal computer or other sound source whereby compensation for imperfections in the hearing of the user may be accomplished. 
     Another object of the present invention is to provide a device having an interactive process provided by a personal computer or other sound source whereby compensation for imperfections in the transducers may be accomplished. 
     These objects are achieved using a system with a headphone or hearing aid unit and a sound source. Programming of the headphone or hearing aid is accomplished using an interactive and iterative process delivered by a personal computer (PC) or similar device. The user is prompted to listen to various signals delivered by the PC thereby testing the frequency response of each ear and headphone combination. Once the testing is completed, individualized compensation factors are created to optimize the listening experience for the user. In the case of a hearing aid device, these compensation factors would be stored within the hearing aids and could be downloaded by wire or by wireless means such as infrared, radio frequency, magnetic or electromagnetic coupling. In headphone units, the compensation factors could be stored within the headphones or at the sound source. In addition, headphone units may be operated by wireless means using infrared, radio frequency, magnetic coupling or other electromagnetic means for both testing and audio listening modes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings forming a material part of this description, there is shown: 
     FIG. 1 illustrating a prior art example of a wired personal audio entertainment device; 
     FIG. 2 illustrating a prior art example of a wireless personal audio entertainment device; and 
     FIG. 3 illustrating a preferred embodiment of the present invention with headphones; 
     FIG. 4 illustrating a preferred embodiment of the present invention with hearing aids. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention allows for compensation of hearing anomalies for both headphone and hearing aid devices. The devices described may also be used to overcome deficiencies within the actual transducer used in the headphone or hearing aid. 
     Refer now to FIG. 3, showing a system overview of one embodiment of the present invention used in conjunction with a headphone system. A personal computer or other sound source  20  is connected by wire to a base unit  22 . The sound source  20  provides both an audio source and a user interface. A preferably wireless headphone unit  14  contains a receiver  30  for downloading information from the base unit  22 , solid-state memory  32  for storing audio characteristic coefficients, signal processing circuits  34  for converting digital information into analog audio signals, amplification system  36  and transducers  38  for converting the amplified audio signals into sound. Wireless transmission  23  between the base unit  22  and receiver  30  is accomplished using infrared, radio frequency, magnetic coupling or other electromagnetic means. 
     To operate the unit, the user chooses a frequency and is prompted to adjust the balance at that frequency until the sound is perceived as centered between the left and right channels. For example, if the left channel is perceived as weaker, balancing will result in boosting the left signal until it is perceived as equal in volume (centered) to the user. The process is repeated at multiple frequencies within the audio spectrum. A simple version would use only bass, midrange and high audio frequencies, while more sophisticated versions could use many more frequencies. With the left and right signals balanced, the user may then be prompted to equalize the system to compensate for perceived differences in amplitude between different frequencies. 
     Upon completion of the balancing and equalization processes, the setting coefficients would preferably be downloaded to the solid-state memory  32  within the headphone unit  14 . Alternately, the coefficients could be stored within the base transmitter or the signal source  20 . The downloaded coefficients are used in conjunction with signal processing circuits  34  such as filters to provide real-time equalization for each ear. Duplex communication between the headphone and base unit is optional and may be used to provide handshaking during download of audio content. In a one-way communication system, a light emitting diode on the headphone unit  14  may be used to indicate successful downloading of data. 
     Refer now to FIG. 4, showing a system overview of a second embodiment of the present invention used in conjunction with a hearing aid system. A personal computer (as shown) or other sound source  20  is connected by wire to a base unit  22 . The sound source  20  provides both an audio source and a user interface. A wireless connection is made to the hearing aid units  24  each containing a receiver  30  for downloading information from the base unit  22 , solid-state memory  32  for storing audio characteristic coefficients, signal processing circuits  34  for transforming digital information into analog audio signals, amplification system  36  and transducers  38  for converting the amplified audio signals into sound. Wireless transmission  23  between the base unit  22  and receiver  30  is accomplished using infrared, radio frequency, magnetic coupling or other electromagnetic means. For example, a first input transducer converts sound waves into analog audio signals. A second transducer converts electromagnetic waves into analog audio signals. 
     Calibration is similar to the headphone unit. The user chooses a frequency and is prompted to adjust the balance at that frequency until the sound is perceived as centered between the left and right channels. The process is repeated at a plurality of frequencies within the audio spectrum. With the left and right signals balanced, the user may then be prompted to equalize the system to compensate for perceived differences in amplitude between different frequencies. Upon completion of the balancing and equalization processes, the setting coefficients are downloaded to solid-state memory  32  within the hearing aid units  24 . The coefficients are used in conjunction with signal processing circuits  34  such as filters to provide real-time equalization for each ear. The signal processing circuits use the coefficient information to correct the amplitude of different frequency spectra of the analog signals (generated by the first or second transducer) resulting in corrected analog audio signals. 
     The hearing aid units  24  may be used in their normal mode to amplify sounds such as speech in proximity of the user  16 . A second mode would allow public address content such as that from a theatre or church to be transmitted to the hearing aid units  24  by magnetic means. This signal would be detected by a detector within the hearing aid units  24 . 
     The present invention is a device and method using an interactive process to improve the listening experience for a user of headphones or hearing aids. The system uses a sound source such as a PC or similar device. Programming of the headphone or hearing aid is accomplished using a process delivered by the sound source. The user is prompted to listen to various signals thereby testing the frequency response of each ear and headphone or hearing aid combination. Once the user testing is completed, individualized compensation coefficients are created to optimize the listening experience for the user. The coefficients are downloaded to and stored within the earpiece. Downloading for hearing aids may be accomplished by wire or by wireless means such as infrared, radio frequency, magnetic or electromagnetic coupling. In headphone units, the compensation factors could be either stored within the headphones or maintained at the sound source. In addition, headphone units may be operated with or without wires (using infrared, radio frequency, magnetic or electromagnetic coupling) for downloading or audio listening. Besides the benefits of improving the auditory perceptual balance over frequency for the individual, this system allows for correction of slightly defective or less costly, inferior transducers. This could bring an economic benefit to the headphone or hearing aid manufacturer. 
     While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the invention.