Abstract: A method for measuring dynamic hardness of elastic materials is applied particularly to determining the state of tonal quality for a piano hammer. The method includes selecting a piano hammer of predetermined type from a set of piano hammers, causing the selected piano hammer to strike against an impact surface having the form of a piano string or string grouping appropriate to a piano hammer of the predetermined type, measuring one or more elements of force and motion of the piano hammer striking the impact surface, e.g. force, determining, e.g., the cut-off frequency of the power spectrum for the selected piano hammer striking upon the impact surface, and comparing the determined cut-off frequency of the power spectrum for the selected piano hammer against a predetermined range of cut-off frequencies of power spectrum acceptable for piano hammer of the predetermined type. An apparatus for testing is also described.

Abstract: A piano key cover having a body of synthetic material pigmented to resemble natural ivory defines a top playing surface having a random orientation of peak-to-valley texture and a multiplicity of fine pores to replicate a surface of natural ivory. A multiplicity of the pores have diameters generally in the range of 0.0002 to 0.0012 inch (0.005 to 0.030 mm). The synthetic material is selected from the group consisting of acrylic polymer, polyurethane, epoxy and the like. A method for forming such a piano key cover and a piano having key covers of the invention are also described.

Abstract: A method for measuring dynamic hardness of elastic materials is applied particularly to determining the state of tonal quality for a piano hammer. The method includes selecting a piano hammer of predetermined type from a set of piano hammers, causing the selected piano hammer to strike against an impact surface having the form of a piano string or string grouping appropriate to a piano hammer of the predetermined type, measuring one or more elements of force and motion of the piano hammer striking the impact surface, e.g. force, determining, e.g., the cut-off frequency of the power spectrum for the selected piano hammer striking upon the impact surface, and comparing the determined cut-off frequency of the power spectrum for the selected piano hammer against a predetermined range of cut-off frequencies of power spectrum acceptable for piano hammer of the predetermined type. An apparatus for testing is also described.

Abstract: A piano key cover having a body of synthetic material pigmented to resemble natural ivory defines a top playing surface having a random orientation of peak-to-valley texture and a multiplicity of fine pores to replicate a surface of natural ivory. A multiplicity of the pores have diameters generally in the range of 0.0002 to 0.0012 inch (0.005 to 0.030 mm). The synthetic material is selected from the group consisting of acrylic polymer, polyurethane, epoxy and the like. A method for forming such a piano key cover and a piano having key covers of the invention are also described.

Abstract: A piano key cover is formed of synthetic material pigmented to resemble natural ivory and having a top playing surface with a random orientation of peak-to-valley texture and a multiplicity of fine pores replicating natural ivory. The key cover is formed by providing a mold, engraving a surface of the mold with a randomly-oriented pattern of peak-to-valley texture replicating natural ivory, placing in the mold a composition of suitable synthetic material pigmented to resemble natural ivory and filler, the filler having the characteristic of being removable from a molded article by further treatment, forming the piano key cover within the mold, and treating the piano key cover to remove the filler thereby causing the surface of the paino key cover to define a plurality of fine pores replicating the surface of natural ivory. A piano including the key cover of the invention, and formed by the above method, is also described.

Abstract: A technique for reducing noise generated by transverse vibrations in elongated members comprises the application of a friction element on a surface of the member. The friction element is forced against one or more surfaces of the member by a selected normal force and is provided in a vicinity of maximum distortion of the member when the member undergoes vibrations. A differential movement between the inner surface of the friction element and the outer surface of the member causes heat to be generated which dissipates the energy of such transverse vibrations.

Abstract: A device for treating flowing working gases in order to reduce their operational noises and in most instances also to increase their operating efficiency comprises a flowing working gas operating device which has a discharge conduit with at least one discharge opening for the outflow of the working gas. A check valve is associated with the discharge and includes an elastic valve member movable to close the opening when the flow thereof decreases to a predetermined amount for example as determined by the reduction of pressure of the gases so as to prevent any back flow into the conduit which is likely to produce noise.

Abstract: A nozzle seal for restricting pneumatic leakage from the nozzle hole of a pneumatic hammer having a tool shank movable therein, comprising, a bushing member and a retaining member axially aligned in the nozzle hole of the pneumatic hammer with a seal member therebetween. Bores are provided through the bushing member, retainer member and seal member for accepting the tool shank with the seal member having a bore closely fit around the tool shank to prevent a leakage of air from the interior of the hammer through the nozzle hole. The bushing member is press-fit and firmly held in the nozzle hole while the retainer member is slip-fit into the hole to facilitate its removal and access to the seal member. The bores may be polygonal, circular or oval to accept tool shanks of corresponding cross-sectional shapes.

Abstract: A muffler construction, particularly for exhaust gases of air-operated tools, comprises, a tubular sleeve having a passage therethrough, an exhaust gas pipe connected into the sleeve and defining a constricted flow passage with the sleeve, first and second opposed cylindrical coaxial shell sections, each having a closed end wall at their respective outer ends and facing in opposite directions engaged with the exhaust gas pipe, and sidewalls spaced radially outwardly from the sleeve. The exhaust gas pipe has a gas pipe discharge and there are partition walls in the shell sections defining a first expansion chamber and at least one additional expansion chamber. A constricted flow passage is defined between the first expansion chamber and the at least one additional expansion chamber with sealing and enclosing members closing the sidewalls of the first and second shell sections so as to define the first expansion chamber and at least one additional expansion chamber within the shell sections.

Abstract: Sudden changes in arc current are slowed to mitigate the resulting noise. A sensor detects large decreases in current during initial stages of arc quench and actuate circuits to maintain ionization and current flow to avoid sharp final drop that causes loud noise impulse. Ionization can be maintained by supplying RF energy at appropriate frequency to the arc electrodes and/or by increasing the arc voltage. The sophisticated control algorithm is implemented utilizing an inexpensive microprocessor to exert proper control of arc sustaining parameters to mitigate arc quenching impulse noise.

Abstract: A reduced operating noise nozzle for a cutting device using at least one electrode and an electric arc to cut material of a workpiece, comprises, a nose end piece disposed around the electrode which has an outer surface tapered from an outer relatively wide diameter end inwardly toward a smaller diameter end which faces the workpiece to be cut. Compressed air is directed in a substantially annular flow path along the tapered surface of the nose piece from the wide diameter end toward the smaller diameter end thereof. Noise which would have emanated from the nozzle, especially when the material of the workpiece which is melted by the arc is blown away to effect the cutting operation, will be greatly reduced.

Abstract: A muffler construction, particularly for exhaust gases of air-operated tools, comprises, a tubular sleeve having a passage therethrough, an exhaust gas pipe connected into the sleeve and defining a restricted flow passage with the sleeve, first and second opposed cylindrical coaxial shell sections, each having a closed end wall at their respective outer ends and facing in opposite directions engaged with the exhaust gas pipe, and sidewalls spaced radially outwardly from the sleeve. The exhaust gas pipe has a gas pipe discharge and there are partition walls in the shell sections defining a first expansion chamber and at least one additional expansion chamber. A constricted flow passage is defined between the first expansion chamber and the at least one additional expansion chamber with sealing and enclosing members closing the sidewalls of the first and second shell sections so as to define the first expansion chamber and at least one additional expansion chamber within the shell sections.