Abstract:
A sound generator includes a memory bank storing user-selectable recorded sounds, a microprocessor that can quasi-randomly time-delay at least one of the recorded sounds, and a mixer that can combine a user-selected recorded sound and the time-delayed sound for output by speakers or earphones. The microprocessor can also cause the output sound to include a microprocessor-selected one of the recorded sounds for inclusion during playback of a user-recorded sound.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to electronic generation of sound, and more specifically to methods and apparatuses that generate sound without generating obviously repetitive identical sound. 
     BACKGROUND OF THE INVENTION 
     Electronic sound generators are often used for personal entertainment, recreation, relaxation and even to promote sleep. Users of such equipment find the sound of rain, falling water, wind, among other natural sounds, to be especially beneficial. The sounds may be used to mask out excessively loud and distracting ambient noise, to soothe the user, and even to help the user fall asleep. 
     Electronic sound generators usually can create several such sounds, and include a switch permitting user-selection of a particular sound. The generators also provide controls for volume and even to permit the user to modulate the effects of some of the sounds. 
     Some electronic sound generators output synthesized sounds. The nature or other sounds will first have been tape recorded, and a digitized representation of the recorded sounds are then electronically stored in a synthesizer integrated circuit (“IC”). The IC is then used in an electronic sound generator to output the user-selected synthesized stored sounds for listening. 
     Other electronic sound generators do not store sounds, but simulate sounds using white noise. Ideally, a “white noise” generator outputs a wide spectrum of frequencies, each frequency component being of equal amplitude. Sounds associated with running or rushing water, for example, may be readily simulated using a white noise generator. The amplitude of the white noise is often modulated, or changed, using a ramp signal. When the instantaneous magnitude of the ramp varies, the magnitude of the white noise sound will be varied. A control can permit the user to vary varying the rate at which the ramp changes amplitude to produce interesting sound effects from white noise electronic sound generators. 
     Whether generated from a single digital synthesizer IC, or from a single white noise source, electronic sound generators present the sound to left and right channel speakers or earphones. This can somewhat improve the sound quality perceived by the user, but nonetheless there is considerable room for improvement. The sounds often sound too “flat”, with too little perception of sound depth or quality. U.S. Pat. No. 5,619,179 (April 1997) to Smith and assigned to the assignee herein discloses a sophisticated method for electronically enhancing the perceived spatial separation of electronically generated sound. Applicants refer to and incorporate herein by reference said &#39;179 patent to Smith, for background material. 
     One problem associated with many electronic sound generators is the somewhat limited repertoire of sounds that are provided and the all too perceivable sensation that the exact same sounds are simply being repeated over and over and over. A listener who selects “raindrop” sounds from an electronic sound generator repertoire soon becomes bored with the generator because after a few seconds, the listener can almost predict what sequence of raindrops falling will be heard next. The sound patterns simply become too repetitious for listening enjoyment or relaxation. 
     In some sound generators, variations in the sounds heard may occur too abruptly. Portions of an ocean wave sound, for example, may transition too abruptly from a quiet and calm wave sound to a loud rushing wave sound. The sensation can be a soft-loud-soft-loud repetitive pattern that is annoying to the user. In fact, some sound patterns that are too repetitively abrupt are believed to trigger seizures in epileptics. 
     In summation, there is a need for an electronic sound generator that can produce sounds whose patterns are not precisely repetitive to where a listener can essentially predict the next sequence in the sound. Such generator should provide a greater variety of perceived sound patterns, including patterns not readily recognizable by a listener as having been heard before. 
     The present invention provides such an electronic sound generator. 
     SUMMARY OF THE INVENTION 
     The present invention reproduces sounds electronically using at least one multi-channel sound integrated circuit (IC). Normally, within the IC different sounds are stored for reproduction through one or two audio channels (e.g., loud speakers). The present invention recognizes that the same stored sound is playable through more than one channel at a time, including playing through more than one channel with time delays. Further, different sounds may be played from different channels and then mixed and output through a single audio channel. 
     In this fashion, a stored digital sound of raindrops may be combined with itself, but with a time delay, to vary the perceived pattern. Further, the raindrop sound may be combined with a segment or “snippet” of other sounds, a bird chirping, for example, to vary the pattern from one playing to another. 
     Other features and advantages of the invention will appear from the following description in which the preferred embodiments have been set forth in detail, in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of an electronic sound generator with enhanced sound, according to the present invention; 
     FIG. 2A is a block diagram depicting use of sound files in a multi-channel IC, according to the present invention; 
     FIG. 2B is a further block diagram depicting use of sound files in a multi-channel IC, according to the present invention; 
     FIG. 2C is a block diagram depicting a preferred use of multiplexed sound files from a multi-channel IC, according to the present invention; 
     FIG. 3A is a block diagram of the preferred implementation of FIG. 2C, according to the present invention; and 
     FIG. 3B is a simplified schematic of the sound generator portion of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 depicts an electronic sound generator  10  with enhanced sound, according to the present invention The preferred embodiment is disposed within a somewhat cylindrical-shaped housing  20  that has a recess area  30  with openings (not shown) from which audible sound generated within by one or more speakers (SPKR(s)) may be heard by a user. 
     Along the top of the housing are several user-controls  40  for selecting particular sounds, e.g., city sounds, roadside sounds, a steam train engine, ocean tide sounds, foghorn sound, dockside sounds, oceanside sounds, surf sounds, rain sounds, brook sounds, waterfall sounds, rainforest sounds, forest sounds, thunderstorm sounds, everglade sounds, campfire sounds, windchimes, summer night sounds, bird sounds, and heartbeat sounds. Of course a different repertoire of sounds could be provided by generator  10 , including a greater or less number of sounds. 
     Also available to the user are various switch controls including an ON/OFF switch S 1  for generator  10 , a sleep switch S 2  that causes sound generator  10  to turn-off after a predetermined time, e.g., 30 minutes, and a volume control (VOLUME) to control volume of the generated sound. 
     Within housing  20  are disposed electronics  100  implementing sound generation according to the present invention, as well as a battery power source B 1 , although DC operating power, e.g., 6 VDC to perhaps 9 VDC, may be generated externally and input to device  10  via input jack J 1 . One or more loud speakers (SPKR(s)) are disposed within the housing, and an earphone jack J 2  permits disabling speaker output in favor of stereophonic audio available to earphones that are connected to J 2 . 
     FIG. 2A depicts a generic multi-channel integrated circuit (IC) chip  110  having a register memory  120  in which are stored a plurality of digitized sounds. Sound  1  may, for example, be city sounds, Sound  2  may be road side sounds, Sound  3  may be steam engine train sounds, and so forth. The stored sounds may have been generated by digitizing authentic sounds, or they may have been synthesized, or perhaps some sounds were digitally recorded and other sounds synthesized. The various sounds in memory  120  are accessible to the various audio channels  130  that are also provided within IC  110 . A given sound may be played through more than one channel at the same time, or through more than one channel using time delays in one or more channels. Thus, Sound  1  is shown being coupled to Channel  2  and, with a time delay, also being coupled to Channel  2 . Sound  3  is shown being coupled directly to Channel  3 . If desired, different sounds can be played from different channels, and then mixed together for output via a common loudspeaker. 
     The configuration of FIG. 2B is used in the present invention to impalement a pseudo-stereo sound. In FIG. 2B, the same sound, e.g., Sound  1  from a common storage address in memory register  120  is played through two audio channels, but with a time delay Δt intentionally inserted in one of the sound paths, here the input to Channel  2 . With Δt equal to a few milliseconds, a reasonably sounding stereo effect can be achieved, especially when the generated sound is heard through stereophonic earphones coupled to input jack J 2  of device  10 . As noted by optional feedback path  140 , the selected channel(s) of audio may be looped back, using techniques known in the art of synthetic sound generator design. 
     An even more sophisticated use of multi-channel IC  110  is depicted in FIG. 2C, wherein “snippets” or sound segments may be combined to generate different combinations of sound. In FIG. 2C, Sound  1  (assume Sound  1  is city sounds) is coupled to Channel  1 . However a time delay Δt 1  later, Sound  2  (assume roadside sounds) is coupled to Channel  2 . At delay time Δt 2 , Sound  3  (assume steam train sounds) is coupled to Channel  3 . At delay time Δt 3  Sound  2  (roadside sounds) is again presented to Channel  2 . The channel outputs, here three channels of audio, are then mixed with mixer  150  and output to a speaker, here the left speaker (if left and right speakers are used) or left earphone audio. The sound heard by a user would start out as city sounds (e.g., perhaps pedestrian noise), and after Δt 1  roadside sounds would be added (perhaps a car horn sounding), then after Δt 2  a steam engine sound might be heard, and after Δt 3  roadside sounds would again be heard. In the preferred embodiment, the various time delays are quasi-randomly within device  10 , and indeed ancillary sounds appropriate for inclusion with primarily selected sounds may be selected by device  10 . While the above description is exemplary, it will be appreciated that a wide variety of sounds may thus be generated, so many sound combinations that the listener is unlikely to “recognize” sound sequences as being exactly identical to previously heard sound sequences. This aspect of the present invention is quite unlike prior art sound generators in which the exact same sound sequences are played to the point where the sound sequences are almost memorized by listeners, who rapidly grow tired of listening. 
     The diagram of FIG. 3A will now be understood in view of the foregoing descriptions. Using various controls on device  10 , a user can select certain sounds and times, for example by pushing control buttons to select foghorn sound, waterfall sound, windchimes sound, and perhaps pushing the sleep button to turn-off the device after a predetermined time period. A central processor unit or microcontroller unit  200  receives the user input and can intelligently augment sound selections by selecting appropriate ancillary sounds. Thus, if foghorn sounds were selected, MCU  200  can decide that some random period Δt 1  into the playing of foghorn sounds that surf sounds may begin to be played as well, since surf sounds and foghorn sounds can previously have been associated within memory in MCU  200 . 
     MCU  200  issues command signals to a master sound chip  1   210 , that contains its own sound and channel registers  120 ,  130 . Sound chip  1  then issues command signals to a slave sound chip  2   220 , that contains its own sound and channel registers  120 ,  130 . The master and slave sound chips  210 ,  220  output their respective audio signals to an audio amplifier unit  230 , and master sound chip  1  also outputs common volume control signals to unit  230  as well. Associated within unit  230  can be mixer  150 . Unit  230  preferably outputs two channels of audio, e.g., to left and right speakers and/or to left and right earphone channels. 
     FIG. 3B is a schematic of the preferred implementation and follows the general block diagram of FIG. 3A, except that the mixer unit  150  is explicitly shown. 
     Modifications and variations may be made to the disclosed embodiments without departing from the subject and spirit of the invention as defined by the following claims. For example, although the present invention had been described with respect to a stand-alone sound generator, the invention could be incorporated into other electronic devices, for example, a CD player, a radio, etc.