Examples of the disclosure describe systems and methods for estimating acoustic properties of an environment. In an example method, a first audio signal is received via a microphone of a wearable head device. An envelope of the first audio signal is determined, and a first reverberation time is estimated based on the envelope of the first audio signal. A difference between the first reverberation time and a second reverberation time is determined. A change in the environment is determined based on the difference between the first reverberation time and the second reverberation time. A second audio signal is presented via a speaker of a wearable head device, wherein the second audio signal is based on the second reverberation time.

Described is a device for creating a sound source comprising integrated measuring means (50) for measuring a property representative of the strength of the sound source, the device comprising a sound generator (40a, 40b) for generating sound within an annular space defined around a central axis, the device comprising a pair of guiding surfaces (113, 123) for guiding sound away from the annular space in opposite directions along the central axis. With sound being guided as described, sound in addition being allowed to propagate outside the device in a radial direction with respect to the central axis, a high degree of omnidirectionality of the created sound source is attained.

Described is a device for creating a sound source comprising integrated measuring means (50) for measuring a property representative of the strength of the sound source, the device comprising a sound generator (40a, 40b) for generating sound within an annular space defined around a central axis, the device comprising a pair of guiding surfaces (113, 123) for guiding sound away from the annular space in opposite directions along the central axis. With sound being guided as described, sound in addition being allowed to propagate outside the device in a radial direction with respect to the central axis, a high degree of omnidirectionality of the created sound source is attained.

An apparatus for estimating an overall mixing time, where the apparatus comprises a processing element configured to determine differences between energy profiles of a first room impulse response of the first pair of room impulse responses and a second room impulse response of the first pair of room impulse responses at a plurality of different sample times of the first pair of room impulse responses, set a sample time of the plurality of sample times as a mixing time for the first pair of room impulse responses at which the difference between the energy profiles of the first room impulse response and the second room impulse response of the first pair of room impulse responses is equal to or below a threshold value, and determine the overall mixing time based on the mixing time for the first pair of room impulse responses.

An apparatus for estimating an overall mixing time, where the apparatus comprises a processing element configured to determine differences between energy profiles of a first room impulse response of the first pair of room impulse responses and a second room impulse response of the first pair of room impulse responses at a plurality of different sample times of the first pair of room impulse responses, set a sample time of the plurality of sample times as a mixing time for the first pair of room impulse responses at which the difference between the energy profiles of the first room impulse response and the second room impulse response of the first pair of room impulse responses is equal to or below a threshold value, and determine the overall mixing time based on the mixing time for the first pair of room impulse responses.

The techniques describe herein use sensor(s) to scan a real-world environment and obtain data associated with geometry of the real-world environment that affects how energy propagates (e.g., locations of spatial objects in a room). The sensor(s) also detect energy (e.g., sound) in the real-world environment, from which a location of a source of the energy can be determined. The techniques combine the geometry data and the energy data to determine how the detected energy propagates from the location of the source through the real-world environment. The techniques can then cause a representation of the propagating energy to be displayed, to a user, as virtual content via a mixed reality device. Accordingly, a user is able to see energy that is otherwise invisible.

Disclosed are a distance rendering method used for audio signal output and an audio signal output apparatus using the same. The distance rendering method includes receiving a decoded audio signal, checking whether a distance between a user and a sound image is changed, if the distance is changed, calculating a gain parameter g.sub.new and a period parameter.sub.new, applied to room response modeling, based on the changed distance, so as to maintain a space characteristic, and generating room response modeling for maintaining the space characteristic even when the distance is changed, using the calculated period parameter .sub.new and gain parameter g.sub.new.

Disclosed are a distance rendering method used for audio signal output and an audio signal output apparatus using the same. The distance rendering method includes receiving a decoded audio signal, checking whether a distance between a user and a sound image is changed, if the distance is changed, calculating a gain parameter g.sub.new and a period parameter.sub.new, applied to room response modeling, based on the changed distance, so as to maintain a space characteristic, and generating room response modeling for maintaining the space characteristic even when the distance is changed, using the calculated period parameter .sub.new and gain parameter g.sub.new.

An apparatus for determining a room dimension estimate including a receiver providing an acoustic room response, a peak detector detects a set of peaks in the acoustic room response in a frequency interval having an upper frequency of no more than 400 Hz, a store includes a set of peak profiles with associated room dimension data, and an estimator determines the room dimension estimate from the associated room dimension data and a comparison of the set of peaks to the peak profiles. The estimator may perform the steps of first finding a matching peak profile for the set of peaks from the set of peak profiles; extracting first room dimension data associated with the matching peak profile(s) from the store; and determining the room dimension estimate in response to the first room dimension data. The peak profiles may represent calculated Eigenfrequencies.

An apparatus for determining a room dimension estimate including a receiver providing an acoustic room response, a peak detector detects a set of peaks in the acoustic room response in a frequency interval having an upper frequency of no more than 400 Hz, a store includes a set of peak profiles with associated room dimension data, and an estimator determines the room dimension estimate from the associated room dimension data and a comparison of the set of peaks to the peak profiles. The estimator may perform the steps of first finding a matching peak profile for the set of peaks from the set of peak profiles; extracting first room dimension data associated with the matching peak profile(s) from the store; and determining the room dimension estimate in response to the first room dimension data. The peak profiles may represent calculated Eigenfrequencies.