# US 8,847,779 B2 · Speaker enclosure design for efficiently generating an audible alert signal > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,847,779 B2 - Document ID: US8847779B2 - Status: Granted - Kind: B2 - Application number: 13/966,055 - Filed: 2013-08-13 - Published: 2013-12-12 - Granted: 2014-09-30 - Earliest claimed: 2009-10-23 - Assignees: Innovalarm Corporation - Applicants: InnovAlarm Corporation - Inventors: Landgrave T. Smith; James J. Lewis; David E. Albert - Web page: https://patentgrep.com/patent/US8847779B2 ## CPC - G08B 17/00: Fire alarms; Alarms responsive to explosion - G08B 3/10: using electric transmission; using electromagnetic transmission - H04R 1/28: Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means {(combinations of transducers with horns, i.e. front-loaded horns H04R1/30)} - G08B 17/113: Constructional details - G08B: SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) ## Abstract Various inventive features are disclosed for efficiently generating regulation-compliant audible alerts, including but not limited to 520 Hz square wave alert/alarm signals, using an audio speaker. One such feature involves the use of a non-linear amplifier in combination with a voltage boost regulator to efficiently drive the audio speaker. Another feature involves speaker enclosure designs that effectively boost the output of the audio speaker, particularly at relatively low frequencies. Some of the disclosed speaker enclosure designs rely on an interference effect and/or a resonance effect to transfer energy from higher-order harmonics downward to the fundamental frequency and lower-order harmonics. These and other features may be used individually or combination in a given alarm-generation device or system to enable regulation-compliant audible alerts to be generated using conventional batteries, such as AA alkaline batteries. ## Claims ### Claim 1 An alarm device, comprising: a sealed speaker enclosure assembly comprising a tubular section, a loudspeaker mounted at one end of and facing outward from the tubular section, and a substantially flat plate that encloses an opposite end of the tubular section, such that a sealed enclosure volume is defined within the tubular section, said loudspeaker comprising a diaphragm driven by a coil; and an alarm signal generation circuit that drives the loudspeaker with an alarm signal that comprises a fundamental frequency and multiple harmonics, said multiple harmonics including a set of low-order harmonics at frequencies above the fundamental frequency and a set of higher-order harmonics at frequencies above the frequencies of the low-order harmonics, said fundamental frequency falling in the range of 400 to 700 hertz; said speaker enclosure assembly configured to cause energy in the second set of higher-order harmonics to be transferred downward in frequency to the fundamental frequency and the set of lower-order harmonics, said transfer caused at least partly by an interference effect in which waves emitted from a rear of the loudspeaker into the tubular section are reflected by the substantially flat plate, causing constructive or destructive interference with waves emitted from a front of the loudspeaker. ### Claim 2 (depends on 1) The alarm device of claim 1, wherein a distance between the loudspeaker and the substantially flat plate is selected such that the interference effect contributes to said transfer of energy. ### Claim 3 (depends on 1) The alarm device of claim 1, wherein the downward transfer of energy is to at least the fundamental frequency and second and fourth harmonics. ### Claim 4 (depends on 1) The alarm device of claim 1, wherein the sealed speaker enclosure assembly is configured to have a resonance frequency that is approximately equal to the fundamental frequency of the alarm signal. ### Claim 5 (depends on 1) The alarm device of claim 1, wherein said downward transfer of energy is caused additionally by a resonance effect resulting in a correspondence between said fundamental frequency and a resonance frequency of the sealed speaker enclosure assembly. ### Claim 6 (depends on 1) The alarm device of claim 1, wherein the tubular section is cylindrical. ### Claim 7 (depends on 6) The alarm device of claim 6, wherein the substantially flat plate is circular and has a diameter in the range of 2 to 3.5 inches. ### Claim 8 (depends on 6) The alarm device of claim 6, wherein the tubular section has a wall thickness in the range of 0.100 to 0.125 inches. ### Claim 9 (depends on 1) The alarm device of claim 1, wherein the loudspeaker has a diameter of approximately three inches. ### Claim 10 (depends on 1) The alarm device of claim 1, wherein the alarm signal is substantially a square wave signal. ### Claim 11 (depends on 10) The alarm device of claim 10, wherein the fundamental frequency is approximately 520 Hz. ### Claim 12 (depends on 1) The alarm device of claim 1, wherein the transfer of energy is based on a comparison of freestanding operation of the loudspeaker to operation of the sealed speaker enclosure assembly. ### Claim 13 (depends on 1) The alarm device of claim 1, wherein the speaker enclosure assembly has a speaker enclosure volume, as measured without the loudspeaker present, of approximately 175 cubic centimeters. ### Claim 14 (depends on 1) The alarm device of claim 1, wherein the tubular section and plate are formed from plastic. ### Claim 15 (depends on 1) The alarm device of claim 1, wherein the tubular section and plate are formed from sheet metal. ### Claim 16 An alarm device, comprising: a sealed speaker enclosure assembly comprising a tubular section, a loudspeaker mounted at one end of and facing outward from the tubular section, and a substantially flat plate that encloses an opposite end of the tubular section, such that a sealed enclosure volume is defined within the tubular section, said loudspeaker comprising a diaphragm driven by a coil; and an alarm signal generation circuit that drives the loudspeaker with an alarm signal that comprises a fundamental frequency and multiple harmonics, said multiple harmonics including a first set of harmonics at frequencies above the fundamental frequency and a second set of harmonics at frequencies above the frequencies of the first set of harmonics, said fundamental frequency falling in a range of 400 to 700 hertz; wherein dimensions of the sealed speaker enclosure assembly, including a length of the tubular section, are selected such that, in comparison to freestanding operation of the loudspeaker, energy is transferred downward in frequency from harmonics in the second set to the fundamental frequency and harmonics in the first set. ### Claim 17 (depends on 16) The alarm device of claim 16, wherein the downward transfer of energy results at least partly from an interference effect in which waves emitted from a rear of the loudspeaker into the tubular section are reflected by the substantially flat plate, causing constructive or destructive interfere with waves emitted from a front of the loudspeaker. ### Claim 18 (depends on 16) The alarm device of claim 16, wherein the downward transfer of energy results at least partly from a resonance effect, said resonance effect resulting from a correspondence between the fundamental frequency and a resonance frequency of the sealed speaker enclosure. ### Claim 19 (depends on 16) The alarm device of claim 16, wherein dimensions of the sealed speaker enclosure assembly, including the tubular section, are selected such that the sealed speaker enclosure assembly has a resonance frequency that is approximately equal to said fundamental frequency. ### Claim 20 (depends on 16) The alarm device of claim 16, wherein the tubular section is cylindrical, and the substantially flat plate is circular. ### Claim 21 An alarm device, comprising: a sealed speaker enclosure assembly comprising a cylindrical section, a loudspeaker mounted at one end of and facing outward from the cylindrical section, and a substantially flat plate that encloses an opposite end of the cylindrical section, such that a sealed enclosure volume is defined within the tubular section, said loudspeaker comprising a diaphragm driven by a coil; and an alarm signal generation circuit that drives the loudspeaker with an alarm signal that comprises a fundamental frequency and multiple harmonics at respective frequencies above the fundamental frequency, said fundamental frequency falling in a range of 400 to 700 hertz; said sealed speaker enclosure assembly, including said cylindrical section, dimensioned such that the speaker enclosure assembly has a resonance frequency that corresponds to said fundamental frequency, said correspondence in frequency producing a resonance effect in which energy in at least some of the harmonics is transferred downward in frequency to at least the fundamental frequency. ### Claim 22 (depends on 21) The alarm device of claim 21, wherein the resonance frequency of the sealed speaker enclosure assembly is dependent upon at least: a diameter of the loudspeaker, a diameter of the cylindrical section, a wall thickness of the cylindrical section, a wall thickness of the plate, and a length of the tubular section. ### Claim 23 (depends on 21) The alarm device of claim 21, wherein the downward transfer of energy is additionally a result of an interference effect in which waves emitted from a rear of the loudspeaker into the cylindrical section are reflected by the substantially flat plate, causing interference with waves emitted from a front of the loudspeaker. ### Claim 24 (depends on 21) The alarm device of claim 21, wherein the transfer of energy is additionally to at least a second harmonic of the alarm signal. ### Claim 25 (depends on 21) The alarm device of claim 21, wherein the sealed speaker enclosure assembly is dimensioned to have a resonance frequency in the range of 450 to 600 hertz. ### Claim 26 (depends on 21) The alarm device of claim 21, wherein the cylindrical section and plate are formed from plastic. ### Claim 27 (depends on 21) The alarm device of claim 21, wherein the cylindrical section and plate are formed from sheet metal. ### Claim 28 (depends on 21) The alarm device of claim 21, wherein the loudspeaker has a diameter of approximately three inches. ### Claim 29 (depends on 21) The alarm device of claim 21, wherein the alarm signal generation circuit comprises a non-linear class D amplifier that receives a power signal from a voltage boost regulator.