Patent Publication Number: US-6983054-B2

Title: Means for compensating rear sound effect

Description:
FIELD OF THE INVENTION 
   The present invention relates to a device for compensating the rear sound effect, and more specifically, to a device that allows the virtual speaker of rear side to be performed by an earphone-like or headphone-like device. 
   BACKGROUND OF THE INVENTION 
   Along with the rapid development of electronic industry, it is not uncommon to play sound effect with advance sound and visual effects on computers anymore. Therefore, the requirement for video and audio performance has become more and more stringent. Except for the need of higher resolution and visual quality, in the field of audio frequency and sound effect, multi-channel sound effect has gradually replaced stereo sound effect and the mono sound effect. In an attempt to provide a more realistic or engulfing listening experience in the home theater, several techniques have developed multi-channel audio formats. Each audio channel of the multi-channel signal is routed to one of several speakers distributed throughout the home theater, providing the sound effect with the sensation that sounds are originating all around them. As the home entertainment system market expands, other multi-channel systems will likely become available to home consumers. Humans are able to localize a sound to the right or left based on arrival time and sound level differences discerned by each ear. 
   Head related transfer functions (HRTFs) are used to simulate positional and virtual images three-dimensional (3-D) sound using fixed speaker locations. The shape of the human head, body and auditory system affect how the brain perceives the position of sound sources. An HRTF is a characterization of the human head, body and auditory system. Thus, the HRTF is affected by the size and shape of the head, the size and shape of the pinnae, the characteristics of the ear canal. The HRTF is typically a function of both frequency and relative orientation between the head and the source of the sound field. The HRTF accounts for the frequency response, frequency filtering, delays and reflections inherent in the human head. By adjusting the frequency and delays of audio signals according to the HRTF, three-dimensional sound can be simulated from fixed speaker locations. U.S. Pat. No. 5,729,612 entitled “Method and apparatus for measuring head-related transfer functions”, which disclosed a method for accurately deriving acoustic transfer functions such as head-related transfer functions at low cost. The prior art is filed on Aug. 5, 1994. 
   A unique HRTF can be calculated for each individual by performing detailed and time-consuming measurements of the head, ear and body. The measurements taken for an individual are converted to a transfer function usable by a processing device to adjust the characteristics of audio signal outputs to individual earphones to simulate positional three-dimensional sound. 
   Because HRTF simulates the sound effect model heard by a human ear in a three-dimensional space and the parameters corresponding to the three-dimensional sound effect at every spot of the space are determined by its distance, azimuth, and elevation, the listener feel like within the real atmosphere of the sound while playing the sound effect. The Head Related Transfer Function uses an artificial head or put microphones within human ears. Each sound source has to be measured from 20 HZ˜20 KHZ and the result is preliminary HRTF library. The preliminary HRTF library, via mathematical process, generates parameters needed by DSP digital filter. As long as mono wave sound is processed by the left and the right digital filters, it can emulate 3D positional audio by means of earphones. 
   HRTF 3D Positional Audio in PC Applications includes simulating multi-speaker Surround with two physical speakers to deliver five “virtual speakers” into space surrounding the listener and enabling home theater sound effects. However, the 5.1 CH DVD or 4 CH 3D game uses HRTF to create virtual speakers on rear side to replace physical speaker for DVD and 3D game meets some problems. The ear-phone device does not have the ability to offer good bass. The bass wavelength is longer than the size of human head, thus there is no direct information on bass due to the structure of the earphone device. Bass speaker called sub-woofer speaker is good for all channels. It is unfortunately, the rear side bass has to be filtered out from rear signal. 
   There is a great need for sound control device to overcome the difficulties mentioned above. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is to disclose a device for compensating the rear sound effect. 
   The further object of the present invention is to provide an earphone-like device to provide virtual speaker of rear side. 
   Means for compensating rear sound effect, comprising: 
   a headphone-like or an earphone-like device with rear speakers carried therein, the headphone-like or earphone-like device including an opening for receiving the front speaker signal, wherein the headphone-like or the earphone-like device includes a housing for receiving the rear speakers, wherein the housings opposite each other, the two housings being joined by a headband, to compose the headphone-like structure; an input plug with conductive wire connected to the housing; and 
   wherein the earphone-like or headphone-like device cannot cover the whole ear for receiving the sound from the front speakers and sub-woofer speaker, the opening allowing the ears to listen the sound from the front speakers, the rear speakers being respectively located on both sides of the earphone-like or headphone-like device to generate the rear channel sound effect of the virtual speaker of rear side. 
   Means for compensating rear sound effect, comprising: 
   main frames for hanging the means on the ears; rear speakers attached on the main frame, the main frames shaped to approximately match the structure of the ears; wherein the main frames opposite each other, the two main frames being joined by wires; an input plug with conductive wire connected to the main frames; and 
   wherein the means for compensating rear sound effect allowing the ear receiving the sound from the front speakers and sub-woofer speaker, the rear speakers being respectively located on both sides of the means for compensating rear sound effect to generate the virtual speaker of rear side with rear bass. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is scheme illustrating a 5.1 D home theater sound effect system according to the present invention. 
       FIGS. 2A–2B  are the device with a headphone-like structure according to the present invention. 
       FIGS. 3A–3B  are the alternative embodiment according to the present invention. 
       FIGS. 4A–4B  are the alternative embodiment according to the present invention. 
   

   THE DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Turning to  FIG. 1 , it illustrates the home theater 5.1D sound effect system  10 , the system  10  includes front right  12 , front left  14 , sub-woofer speakers  16  and rear right, rear left speakers  20 . One of the aspects of the present invention is that the rear right, rear left speakers are constructed by an earphone-like or headphone-like device or structure. The feature of the present invention focus on the rear speakers and the control system. It has to be noted that the rear speakers are consisted in the earphone-like structure for user to carry on one&#39;s head instead of positing on a certain locations to create the virtual speakers of rear side. The earphone-like or headphone-like device cannot cover the whole ear for receiving the sound from the front speakers and sub-woofer speaker. Thus, there is opening structure to allow the ears to listen the sound from the front speakers. The rear right and rear left speakers are respectively located on both sides of the earphone-like or headphone-like device to create the virtual speakers of rear side sound effect. 
   Means for creating HRTF is coupled to the rear right and left signal to process the signal that transmitted to the rear right and left speaker carried by the earphone-like or headphone-like structure. It is because that the distant of the rear right and left speaker to the ear is closer than the distant of other speakers. Thus, means for creating virtual speaker of rear side is connected to the means for generating HRTF. Typically, the delay time is approximately D/velocity of sound in the air. The processed signal is fed to the volume controller for adjusting the output volume. HRTF simulates the sound effect model heard by a human ear in a three-dimensional space and the parameters corresponding to the three-dimensional sound effect at every spot of the space are determined by its distance, azimuth, and elevation. 
   Then, the signal is fed to an amplified therefore output by the rear speakers carried by earphone-like or headphone-like structure. The signal performed by the rear speakers is delay and therefore the ear may receive the signal from the rear speaker and front speaker at the same time. Alternatively, the signal under transmitting to the rear speaker may be emitted by IR or RF. Thus, the earphone-like or headphone-like structure needs the receiver to receive the wireless transmission signal. 
   FIGS  2 A– 2 B illustrate the structure according to the present invention. In the present invention, the present invention provides a headphone-like or earphone-like device  100  with rear speakers  110  carried therein. The headphone-like or earphone-like device  100  includes an opening  120  for receiving the front speaker signal. The sound effect system transmits the front, rear and sub-woofer signal to the associated speakers. The signal under transmitting to the rear speakers is delay according to the distance between the user and the front speaker. 
   The present invention provides a headphone-like or earphone-like device for the user to carry on one&#39;s head. The headphone-like device includes a housing  130  for receiving the rear speaker  110 . The housings  130  opposite each other, the two housings are joined by a headband  140 , to compose a headphone-like device  100 . An input plug  150  with conductive wire  160  is connected to the housing  130 . If the structure without the transmission line, the housing  130  contains a wireless signal receiver therein. 
   Another structure is illustrated in  FIG. 3A-3B , the device includes main frames  310  for hanging the device on the ears. The rear speakers  320  are attached on the suitable position of the main frame  310 . The main frames  310  are shaped to approximately match the structure of the ears. The main frames  310  opposite each other, the two main frames  310  are joined by wires  340 . An input plug  330  with conductive wire  340  is connected to the main frames  310 .  FIG. 4  is another alternatively embodiment according to the present invention. The embodiment is useful for the one who wears the eyeglass  400 . As shown in  FIGS. 4A and 4B , the rear speakers  420  are attached on the eyeglass frame  430 . The present invention is attached by slidable adjustable means, such as the elastic loop  412  to a respective one of the frame  430 . The adjustable means permits the positioning of the rear speaker support frame  410  along the directions of arrows  15  to a suitable position. Typically, the user wears the eyeglass  400  on the ears  416 , the rear speaker  420  extends from the support frame to the upper portion of the ear structure as shown in the  FIG. 4B . The rear speaker located at the position will provide better sound effect. An input plug with conductive wire  500  is connected to the support frame  410 . 
   The present invention provides virtual speaker of rear side without concerning the losing of the rear bass. 
   As is understood by a person skilled in the art, the foregoing preferred embodiments of the present invention are illustrated of the present invention rather than limiting of the present invention. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structure. While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.