1. Field of the Invention
The present invention relates to a method and instrumentation for detecting, locating and diagnosing sounds generated by internal combustion engines and other machinery having rotating and moving parts. More particularly, the invention is directed to electronic diagnostic instrumentation for locating the source and cause of trouble indicating sounds in engines and machinery having rotating and moving parts.
2. Description of The Prior Art
Internal combustion engines, diesel engines, generators, compressors, pumps and numerous other types of machinery having rotating and moving parts generate a multiplicity of acoustic signals and sounds which, in combination, are referred to as engine or machinery noise. This is particularly true of automotive engines. Individual sound components of automotive engine noise, when separated, may be used to detect the existence, location and cause of an engine abnormality such as a piston knock, valve clatter, pressure leak, bearing and bushing failure, broken or chipped gear teeth or frictional abrasion. Further, sound components of the engine's environment may indicate exhaust manifold leaks, wind and water leaks, and pressure and vacuum leaks. Thus, for the proficient auto mechanic it is necessary to be able to discriminate between the acoustic signals and sounds forming the noise pattern of operating engines and engine environments and to locate the source of and cause of such signals and sounds.
In the past a number of methods have been utilized to accomplish sound discrimination and cause in internal combustion engines and other types of machinery. Most simply and basically, the auto or other mechanic has used his or her ears to listen for particular types of sound such as engine and engine accessory knocking, clinking, clattering, screeching and the like, and to move an ear toward or away from various areas of the operating engine so as to detect the increase or decrease in level of a particular sound or signal. The source of the particular knock, clink or clatter sound is thus determined by searching for the general area of the engine from which the sound appears (by hearing sense) to be emanating with the greatest intensity. This crude method of sound location has many objections including the danger of body contact with rotating engine parts and hot exhaust ducts. Many areas of the engine and its associated systems which generate noise are difficult to reach in terms of hearing proximity and thus to pinpoint sound sources and causes. Further, it is often difficult to locate the source of a particular sound with this crude detection method because of echo effects and low level abnormal signals are masked by louder engine noises. Finally, certain abnormal sound vibrations may fall outside of the audible frequency range of a mechanic's hearing capacity.
A second commonly used engine sound discrimination method has involved the use of an elongated and flexible rubber or plastic tube of which one end is inserted into the mechanic's ear with the other tube end moved by hand to various areas and parts of the operating engine so as to isolate the source of a particular type of engine sound. This crude method also has disadvantages because the hand manipulated end of the sound tube cannot be brought into close proximity to hot pipes, ducts and surfaces of the engine system or to rotating engine parts without the danger of injury to the mechanic's hand. Also, there is the drawback of this method that certain types of acoustic signals may not couple effectively with the hand-held, open end of the sound tube or propagate through the interior of the tube without sound energy loss so that the signals are not detectable at the ear end of the tube.
Another classic and crude method for engine noise discrimination, particularly used to find the source of a screeching sound which usually indicates a faulty bearing in a water pump, alternator, air conditioner compressor, or other rotating engine part, is for the mechanic to hold a screwdriver in his or her mouth and to contact the driver bit portion of the screwdriver to various parts of the engine system to feel for low level vibrations. Thus, engine system vibrations are transmitted through the screwdriver and mechanic's jawbone system to the ear where they can be detected without concern for masking by engine and engine compartment echoes. This method of noise detection also has numerous drawbacks and dangers including facial harm from rotating and hot engine parts and exposure of the mouth and eyes to engine dirt.
Eventually, auto mechanics recognized the value of the simple medical-type stethoscope as a device for detecting, locating and diagnosing sounds generated by internal combustion engines. In recent years the basic principals of the more sophisticated medical electronic stethoscope, for detecting and discriminating between human auscultatory sounds, have been applied to devices for detecting acoustical signals and sounds generated by engine systems. Thus, an electronic stethoscope with a sound probe (coupled to an earphone headset) for detecting automotive engine sounds to locate potential mechanical faults (valve chatter, tappet noise, piston slap, gear and pump noises, etc.) has been supplied to the professional auto maintenance field since 1987 by Transcat of Rochester, N.Y. In 1989 JS Products, Inc. of Las Vegas, Nev. introduced the "EngineEAR" as an improved electronic stethoscope or listening tool for use by the automotive maintenance profession. This device included a sensitive microphone at the tip end of an extended flexible probe arm.
It is a principal object of the present invention to provide a new and improved acoustic signal and sound diagnostic tool for the professional automotive engine and industrial machinery maintenance field to detect with greater sensitivity and accuracy the existence, location and cause of operating engine and machinery abnormalities and engine and machinery environmental abnormalities.
It is a further object of the invention to provide a new and improved electronic listening tool for the professional engine and machinery mechanic which is capable of discriminating with greater sensitivity the acoustic signals and sounds forming the noise patterns of operating engines and machinery and to locate the source of and cause of such signals and sounds.
It is a still further object of the invention to provide a new and improved acoustic signal and sound diagnostic instrument with an ultra-sensitive, transducer-type sound pick-up at the tip of an extended flexible and positionable probe arm (for direct contact with operating engine and machinery parts) coupled through electronic circuitry to an earphone headset for audible sound discrimination and to visual means for indicating changes and peaks in sound level and average values of sound level.
Other objects and advantages of the invention will be apparent to those skilled in the professional engine and machinery maintenance field from the following summary and detailed description of the acoustic signal and sound diagnostic instrument of the invention taken together with the accompanying drawing figures.