# US 12,009,877 B1 · Modification of signal attenuation relative to distance based on signal characteristics > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,009,877 B1 - Document ID: US12009877B1 - Status: Granted - Kind: B1 - Application number: 16/937,433 - Filed: 2020-07-23 - Granted: 2024-06-11 - Earliest claimed: 2019-09-05 - Assignees: Apple Inc. - Applicants: Apple Inc. - Inventors: Christopher T. Eubank; Tomlinson Holman; Martin E. Johnson - Web page: https://patentgrep.com/patent/US12009877B1 ## CPC - H04B 17/318: Received signal strength - H04R 3/12: for distributing signals to two or more loudspeakers {(specially adapted for hearing aids H04R25/407)} - H04R 5/033: Headphones for stereophonic communication {(details thereof, e.g. relating to batteries, cables or control elements H04R1/10)} - H04R 5/04: Circuit arrangements, {e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments (combinations of amplifiers H03F3/68; stereophonic systems H04S)} - H04S 7/304: {For headphones} - H04S 2420/01: Enhancing the perception of the sound image or of the spatial distribution using head related transfer functions [HRTF's] or equivalents thereof, e.g. interaural time difference [ITD] or interaural level difference [ILD] - H04B: TRANSMISSION - 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) - H04S: STEREOPHONIC SYSTEMS ## Abstract Spatializing audio can include determining a draw-away curve of an audio signal and modifying the draw-away curve based on a strength of the audio signal. The strength can be determined prior to spatializing the audio signal. The audio signal can be attenuated or modified based on the modified draw-away curve. The attenuated or modified audio signal can be spatialized. Other aspects are described and claimed. ## Claims ### Claim 1 A method comprising: determining a first relationship, based on one or more acoustic characteristics of a virtual space, between a) strength of an audio signal of a sound source as perceived by a listener, and b) distance between the sound source and the listener in the virtual space; determining a strength of the audio signal of the sound source; determining a second relationship between a) the strength of the audio signal of the sound source as perceived by the listener, and b) the distance between the sound source and the listener in the virtual space that is different from the first relationship, based on the determined strength of the audio signal, by decreasing or increasing the strength of the audio signal as perceived by the listener at one or more distances between the sound source and the listener as defined by the first relationship; determining a strength of a modified audio signal based on the second relationship and a current distance between a current position of the sound source and a current position of the listener in the virtual space; and spatializing the modified audio signal, based on the current position of the listener and the current position of the sound source in the virtual space, with a head related transfer function, resulting in a left and right spatialized audio signal, that, when used to drive a left speaker and a right speaker of a headphone set, are converted to sound that is perceived by the listener to contain the sound source at the current position of the sound source in the virtual space. ### Claim 2 (depends on 1) The method of claim 1, wherein the one or more acoustic characteristics includes a geometry that defines an enclosed space, including one or more walls, a ceiling, or a volume of the virtual space. ### Claim 3 (depends on 1) The method of claim 1, wherein the one or more acoustic characteristics includes reverberation time of the virtual space. ### Claim 4 (depends on 1) The method of claim 1, wherein the one or more acoustic characteristics indicates an open area without walls or ceilings. ### Claim 5 (depends on 1) The method of claim 1, wherein the one or more acoustic characteristics includes sound absorption or scattering parameters of the virtual space. ### Claim 6 (depends on 1) The method of claim 1, wherein the one or more acoustic characteristics includes definition of how many sound sources are present in the virtual space. ### Claim 7 (depends on 1) The method of claim 1, wherein the first relationship between a) the strength of the audio signal of the sound source as perceived by the listener and b) the distance between the sound source and the listener in the virtual space is further determined based on a directivity of the sound source. ### Claim 8 (depends on 1) The method of claim 1, wherein the method is repeated periodically to dynamically determine additional relationships and additional modified audio signals over time. ### Claim 9 (depends on 1) The method of claim 1, wherein the second relationship does not change a current strength of the audio signal as perceived at the current position of the listener, and does change the strength of the audio signal as perceived at farther or closer positions from the sound source in the virtual space, when the second relationship is used to determine the strength of the modified audio signal. ### Claim 10 (depends on 1) The method of claim 1, wherein determining the second relationship is further based on a type of the sound source, movement parameters of the listener or the sound source, or a number of sound sources in the virtual space. ### Claim 11 (depends on 1) The method of claim 1, wherein determining the strength of the modified audio signal includes a) applying an inverse of the second relationship to the current distance between the sound source and the listener in the virtual space, to determine the modified strength at the current distance, or b) applying an attenuation that corresponds to the current distance between the sound source and the listener to the audio signal. ### Claim 12 (depends on 1) The method of claim 1, wherein the strength of the audio signal is one of, or a combination of: a physical loudness of the audio signal, and a perceptual loudness. ### Claim 13 (depends on 12) The method of claim 12, wherein the physical loudness is a measure of one or more of the following: a root mean squared (RMS) loudness, an average loudness, or a peak loudness, over one or more time frames of the audio signal. ### Claim 14 (depends on 12) The method of claim 12, wherein the perceptual loudness is a measure of one or more of the following: A-weighting loudness, or Loudness K-weighted relative to full scale (LKFS). ### Claim 15 (depends on 1) The method of claim 1, wherein determining the first relationship includes calculating a draw-away curve of the sound source, the draw-away curve having a) a direct sound component, and b) a reverberant component. ### Claim 16 (depends on 1) The method of claim 1, wherein determining the second relationship includes tapering or compressing the first relationship beyond but, not prior, to a threshold proximity to the sound source. ### Claim 17 (depends on 1) The method of claim 1, wherein determining the second relationship includes reducing the strength of the audio signal as perceived by the listener at one or more distances to maintain the strength of the audio signal, or a combined strength of multiple audio signals of multiple sound sources, below threshold criteria that is specified based on protection of a human ear, or a hardware limit. ### Claim 18 (depends on 1) The method of claim 1, further comprising: determining a third relationship between a) strength or attenuation of a second audio signal of a second sound source as perceived by the listener, and b) distance between the second sound source and the listener in the virtual space, based on the one or more acoustic characteristics of the virtual space; determining a strength of the second audio signal; determining a third modified relationship based on the determined strength of the second audio signal, by decreasing or increasing the strength of the second audio signal as perceived by the listener or the attenuation of the second audio signal at one or more distances between the second sound source and the listener as defined by the third relationship; determining a strength of a second modified audio signal based on the third modified relationship and a current distance between a current position of the second sound source and the current position of the listener in the virtual space; and spatializing the second modified audio signal, based on the current position of the listener and the current position of the second sound source in the virtual space, resulting in second left and right spatialized audio signals that, when combined with the left and right spatialized audio signals, and used to drive the left speaker and the right speaker of the headphone set, are converted to sound that is perceived by the listener to contain the sound source and the second sound source at respective positions in the virtual space. ### Claim 19 A system for spatializing audio, comprising: a processor; and non-transitory memory having stored therein a plurality of instructions, that when executed by the processor, perform the following: determining a baseline relationship between a) strength of a direct component of an audio signal of a sound source as perceived by a listener, and b) distance between the sound source and the listener in a virtual space, based on one or more acoustic characteristics of the virtual space; calculating strength of audio signal; determining, based on the calculated strength of the audio signal, a modified relationship between a) the strength of the audio signal of the sound source as perceived by the listener, and b) the distance between the sound source and the listener in the virtual space that is different from the baseline relationship, by decreasing or increasing the strength of the direct component at one or more distances between the sound source and the listener defined by the baseline relationship; determining a strength of a modified direct component based on a) the modified relationship of the direct component and b) a current distance between a current position of the sound source and a current position of the listener in the virtual space, resulting in a direct component of the audio signal having an attenuated strength; and determining a reverberant component of the audio signal, based on the one or more acoustic characteristics of the virtual space; determining a reverberant attenuation level, based on the calculated strength of the audio signal attenuating the audio signal with the reverberant attenuation level, resulting in a reverberant component with attenuated strength; and spatializing and combining the modified direct component and the reverberant component having the attenuated strength, based on a current listener position and current sound source position in the virtual space, with a head related transfer function, resulting in left and right spatialized audio signals, that, when used to drive a left speaker and a right speaker of a headphone set, are converted to sound that is perceived by the listener to contain the sound source and the second sound source at respective positions in the virtual space. ### Claim 20 An article of manufacture, comprising: a processor; and non-transitory memory having stored therein a plurality of instructions, that when executed by the processor, perform the following: determining, based on one or more acoustic characteristics of the virtual space, a baseline draw-away curve of a sound source that defines strength or attenuation of an audio signal of a sound source relative to a distance between the sound source and the listener in a virtual space; calculating strength of an audio signal of a sound source; modifying, based on the calculated strength of the audio signal, the strength or the attenuation of the audio signal relative to the distance between the sound source and the listener in the virtual space defined by the baseline draw-away curve, resulting in a modified draw-away curve that is different than the baseline draw-away curve; determining a modified audio signal based on the modified draw-away curve and a distance between a current position of the sound source and a current position of the listener in the virtual space; and spatializing the modified audio signal based on a current listener position and current sound source position in the virtual space, with a head related transfer function, resulting in a left and right spatialized audio signal, that, when used to drive a left speaker and a right speaker of a headphone set, are converted to sound that is perceived by the listener to contain the sound source at the current sound source position in the virtual space.