Method and system for detecting drowsiness and / or sleep - Patent Application 20070122997

Abstract

A method and system are provided for detecting drowsiness and / or sleep and controlling the volume of audio delivered, for example, from an in-ear speaker. An outer ear pressure detected between the eardrum and the in-ear speaker is acquired and processed together with the frequency and amplitude characteristics of the delivered audio. In this manner, a baseline ear pressure over time is obtained. Drowsiness and / or sleep can be detected from the derived baseline ear pressure, so that, for example, the volume of the delivered audio can be adapted accordingly.

Description

[Technical Field]

[0001] The present invention relates to the detection of drowsiness and / or sleep. For example, such detection can be used to control the sound delivered by in-ear speakers, in particular to provide automatic power-off when the listener is asleep. Such detection can also be used to control other external devices. [Background technology]

[0002] Music has always been an essential element of modern culture. Advances in digital technology have made it possible to listen to music anytime, anywhere using personal listening devices (PLDs) such as iPods, mobile phones, and tablet computers. Summary of the Invention [Problem to be solved by the invention]

[0003] Music has been shown to have beneficial effects and has been used as part of music therapy to manage many neurological and psychiatric disorders. However, recent scientific studies have shown that excessive music exposure on a PLD may induce hearing loss or accelerate age-related hearing loss. The prevalence of hearing loss due to music exposure in young adults has been reported to range from 9.3% to 14%.

[0004] Furthermore, it has been observed that approximately 58% of adolescents and college students exceed the recommended maximum noise exposure while listening to music. Music volume level as well as total exposure time have been observed to be significantly correlated with hearing loss. If not detected and treated in time, hearing loss from such exposure can be permanent.

[0005] PLDs are often used with in-ear speakers, i.e., earplugs / earphones. Many people fall asleep listening to music. In such situations, continuous and prolonged exposure to music can be harmful to the ears.

[0006] It has been proposed to automatically reduce the volume of music when sleep is detected. For example, International Publication No. 2012 / 058886 and Chinese Patent Application Publication No. 109561219 each disclose using pressure detection to detect pulse and identifying sleep from pulse characteristics such as heart rate variability.

[0007] However, pulse detection may not be accurate because the heartbeat may be drowned out by, for example, the music you are listening to, which may even have a rhythm that corresponds to your pulse rate. [Means for solving the problem]

[0008] The invention is defined by the claims.

[0009] An embodiment according to one aspect of the present invention provides a method for detecting drowsiness and / or sleep, the method comprising the steps of receiving an outer ear pressure sensed between the eardrum and the in-ear speaker from a pressure sensor forming part of the in-ear speaker while audio is being delivered to the in-ear speaker, processing the frequency and amplitude characteristics of the delivered audio and the outer ear pressure to derive a baseline ear pressure over time, and detecting drowsiness and / or sleep from the derived baseline ear pressure.

[0010] This method uses pressure sensing to detect drowsiness and / or sleep. Instead of using pressure sensing to detect pulse in known ways, a baseline (residual) pressure is obtained by separating the pressure resulting from the subject's physiology from the pressure generated by audio. The baseline pressure is the pressure resulting from the subject's physiology after subtracting the pressure effect of music (or other audio) being listened to. The baseline pressure allows for the detection of various events, such as short-term pressure changes due to yawning or gradual pressure changes over time.

[0011] Audio data for the transmitted audio is received, and frequency and amplitude characteristics of the transmitted audio are processed using the audio data. A baseline ear pressure is obtained by subtracting the pressure effect of the audio being listened to from the detected outer ear pressure.

[0012] The detected drowsiness and / or sleep can be used to control the device, for example, to turn the device off or to reduce the volume. For example, in response to detected drowsiness or sleep, the volume delivered by the in-ear speaker itself can be reduced or the audio can be turned off (i.e., the volume is adapted to zero). The volume can also be reduced gradually to zero.

[0013] At its simplest level, the method can be implemented without the need for any dedicated external sensors for detecting sleep or drowsiness states. Instead, basic hardware present in the in-ear speaker itself is used for sleep detection. The acoustic transducer within the earphone can be reversed to function as a microphone for detecting pressure changes. To this end, duty cycle control can be used to alternate between speaker and pressure sensor (i.e., microphone) functions.

[0014] The method may include, for example, applying a timestamp to the audio and the detected ear pressure using a shared clock, so that the different signals can be synchronized for analysis.

[0015] Detecting drowsiness and / or sleep includes detecting a yawn event from the baseline ear pressure and / or detecting an increase in middle ear pressure associated with sleep from the baseline ear pressure.

[0016] Yawning signals the onset of sleep. The frequency of yawning events can be monitored over time, for example. Middle ear pressure is known to increase during sleep, and this can be detected from the measured outer ear pressure by separating the audio pressure from the baseline pressure.

[0017] The method may further comprise detecting a correct fitting of the in-ear speaker to the ear and generating an output signal indicative of an incorrect fit.

[0018] Pressure sensing requires the formation of a closed cavity to allow accurate measurement and interpretation of baseline pressure measurements, so that in the event of an incorrect fit, a warning can be provided and / or sleep detection-based controls can be overridden.

[0019] The method may further comprise sensing outer ear pressure during the calibration phase to determine subject-specific pressure characteristics.

[0020] This allows the analysis of the baseline pressure to be more accurate for a particular subject. The calibration phase may involve, for example, the subject performing tasks such as (simulated) yawning, swallowing, and / or jaw movements. This calibration phase may also be used to detect ear pathologies.

[0021] Deriving baseline ear pressure over time can include using an analytical model of the ear canal, which takes into account the volume and shape of the ear canal cavity.

[0022] The analytical model is constructed for the subject by, for example, sensing one or more ear canal size or shape characteristics.

[0023] Proximity or ultrasonic sensors can be used for this purpose. The model can also take into account, for example, the age and sex of the subject.

[0024] The method may further include sensing movement of the subject using the inertial monitoring unit and additionally detecting drowsiness and / or sleep from the sensed movement.

[0025] This monitors head movement while listening to audio. As a person becomes drowsy, their head movement is expected to decrease and eventually the head will stabilize in a particular position for a period of time. Head movement can then be correlated with baseline pressure changes to detect drowsiness or sleep. The inertial monitoring unit can form part of the in-ear speaker.

[0026] The present invention provides a method of controlling a device, the method comprising the steps of detecting drowsiness and / or sleep, and controlling the device dependent on the detection of drowsiness and / or sleep. The controlled device may be the in-ear speaker itself (e.g. by controlling an audio source sending audio to the in-ear speaker), an external device such as a television, or a non-audio device such as a lighting device, a heating device, a device putting a mobile phone into "sleep mode", etc.

[0027] Thus, in one example, the device has in-ear speakers and controlling the device includes adapting the volume (or on / off state) of the audio being delivered in response to the detection of drowsiness and / or sleep.

[0028] The method may further comprise detecting an awakening from sleep and controlling the delivery of audio by the in-ear speaker to improve sleep quality. The awakening from sleep may be detected by an inertial monitoring unit of the mobile phone or other sensors such as an EEG sensor. When an awakening is detected, other devices may be controlled, for example a coffee machine.

[0029] The method may further comprise controlling a valve to vent a space between the eardrum and the in-ear speaker to the ambient environment in response to detecting drowsiness and / or sleep.

[0030] The valve provides a physical connection that, when opened, creates an air passage between the ear canal and the outside, so that the ear canal is no longer a closed cavity. This connection can be opened when the audio volume is turned down or off. This reduces humidity in the ear canal and establishes near-normal airflow, thus reducing the risk of infection.

[0031] The invention also provides a computer program having a computer program code configured to perform the above-described method when the computer program runs on a computer.

[0032] The present invention further provides a drowsiness and / or sleep detection system comprising an in-ear speaker having a pressure sensor that detects outer ear pressure between the eardrum and the in-ear speaker, and a processor, the processor configured to receive the detected outer ear pressure from the pressure sensor, process frequency and amplitude characteristics of audio delivered to the in-ear speaker and the corresponding detected outer ear pressure to derive a baseline ear pressure over time, and detect drowsiness and / or sleep from the derived baseline ear pressure.

[0033] The processor is configured to detect drowsiness and / or sleep, for example, by detecting a yawn event from the baseline ear pressure and / or detecting an increase in middle ear pressure associated with sleep from the baseline ear pressure.

[0034] The present invention further provides an audio delivery system having a drowsiness and / or sleep detection system as defined above, wherein the processor is configured to adapt the volume (or on / off state) of the delivered audio in response to the detection of drowsiness and / or sleep.

[0035] The system (for drowsiness detection or audio delivery) may further comprise a sensor device for detecting correct fitting of the in-ear speaker to the ear, the processor being configured to generate an output signal indicative of when the fitting is not correct.

[0036] The system (for drowsiness detection or audio delivery) may further comprise an inertial monitoring unit, the processor being configured to additionally detect drowsiness and / or sleep from the detected movements.

[0037] The audio delivery system may further comprise a sensor device for detecting arousal from sleep, in which case the processor is configured to control the delivery of audio in response to detecting arousal from sleep to improve sleep quality.

[0038] The system (for drowsiness detection or audio delivery) may further comprise a valve for venting the space between the eardrum and the in-ear speaker to the ambient environment, in which case the processor is configured to control the valve in response to detection of drowsiness and / or sleep.

[0039] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0040] For a better understanding of the present invention and to show more clearly how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: [Brief explanation of the drawings]

[0041] [Figure 1] FIG. 1 illustrates an audio transmission system. [Figure 2] 1 illustrates a calibration phase of a method for controlling the volume of audio delivered from an in-ear speaker. [Figure 3] FIG. 10 illustrates a volume control method after a calibration phase. [Figure 4] FIG. 1 shows a plot of baseline pressure over time and a single yawn event. DETAILED DESCRIPTION OF THE INVENTION

[0042] The present invention will now be described with reference to the drawings.

[0043] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the devices, systems, and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the devices, systems, and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the drawings are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the drawings to indicate the same or similar parts.

[0044] The present invention provides a method and system for detecting drowsiness and / or sleep and then controlling the volume of audio delivered, for example, from an in-ear speaker. The outer ear pressure detected between the eardrum and the in-ear speaker is acquired and processed along with the frequency and amplitude characteristics of the delivered audio. In this way, a baseline ear pressure over time is obtained. Drowsiness and / or sleep can be detected from the derived baseline ear pressure and, for example, the volume of the delivered audio can be adapted accordingly.

[0045] FIG. 1 shows an audio delivery system 10 that includes an in-ear speaker 20 with a pressure sensor 22 that detects outer ear pressure between the eardrum and the in-ear speaker 20 .

[0046] Audio is sent to system 10 from audio source 30. Typically, audio source 30 is a mobile phone or music player, and communication between the audio source and system 10 is via short-range wireless communication such as Bluetooth®. Of course, a wired connection is also possible.

[0047] The system's processor 24 receives the sensed outer ear pressure from the pressure sensor 22 and also analyzes the frequency and amplitude characteristics of the audio sent to the in-ear speakers. Optionally, the system further comprises an inertial monitoring unit (IMU) 26.

[0048] The processor's functions are shown in Figure 1.

[0049] A first module 40 receives the sensed outer ear pressure from the pressure sensor 22 and also receives the audio data. A second module 42 extracts the component resulting from the audio itself from the sensed outer ear pressure. In this way, a baseline ear pressure over time is derived. This baseline ear pressure is derived from the listener's physiology.

[0050] A second module 42 processes the baseline ear pressure to detect drowsiness and / or sleep, and a third module 44 of processor 24 then generates a volume control signal V to adapt the volume of the transmitted audio depending on the detection of drowsiness and / or sleep. The volume control signal V is returned to audio source 30.

[0051] 1 shows a single in-ear speaker, but of course a system will typically have a pair of in-ear speakers, and sleep detection can be implemented in one or both in-ear speakers.

[0052] Figure 2 shows the first steps of a method for controlling the volume of audio delivered through in-ear speakers. The steps of Figure 2 can be considered part of a calibration phase before a user of the system uses the speakers to listen to audio.

[0053] In use, at step 50, the in-ear speaker is inserted into the outer ear, sealing the ear canal from the outside air. This essentially creates a closed cavity. The pressure sensor 22 is on one side of the cavity and the eardrum is on the other side of the cavity.

[0054] In step 52, outer ear pressure is detected and monitored over time, while the subject is asked to perform several simple actions, such as swallowing, yawning, and dropping their jaw, in step 54. These actions cause pressure changes in the outer ear, which are analyzed in step 56. This information is used as a baseline for subsequent processing.

[0055] This information is further used to detect that the in-ear speakers are correctly positioned and functioning and to allow measurement of the baseline pressure in the ear canal in step 58. If the in-ear speakers are not working properly, this can be indicated in step 60 using an audiovisual indicator.

[0056] Pre-existing pathologies of the outer ear can also be checked by analyzing pressure changes in the outer ear. If any pre-existing pathologies are present, this can again be indicated by an audiovisual indicator.

[0057] For example, detection of a tympanic membrane perforation is performed in step 62 and, if present, this is indicated by an audiovisual indicator in step 64 .

[0058] Detection of other pathologies is performed in step 66 and, if present, this is indicated by an audiovisual indicator in step 68 .

[0059] The above calibration step is optional: although calibration is preferred to adapt the system to individual subjects, detection of pathologies is entirely optional.

[0060] FIG. 3 shows the volume control method after the calibration phase.

[0061] In step 70, the user turns on the audio, which automatically activates the pressure sensor, which then measures the pressure in step 72. The pressure in the outer ear is monitored in real time and is denoted P_Measured.

[0062] The audio being played creates sound waves that travel through the air by displacing a nearby column of air in the ear canal, which is sealed on one end by the in-ear speaker and on the other by the eardrum, which changes the pressure within the ear canal.

[0063] The pressure change in the ear canal depends on both the frequency and amplitude of the sound waves resulting from the reproduced audio, as well as the physical dimensions of the ear canal. The ear canal is generally an elliptical cylinder, approximately 25 mm long and 7 mm in diameter. To measure the pressure change, a lossless cylindrical tube model was proposed as an approximation of the ear canal. Therefore, the volume of the closed cavity created by an in-ear speaker can be calculated as follows: V=πr2h (1) where h is the distance between the pressure sensor and the eardrum, and r is the radius of the ear canal. Standard values ​​can be used for h and r, for example, based on age and gender. However, precise values ​​can also be used by using appropriate sensors, such as proximity sensors, ultrasonic sensors, etc.

[0064] The audio characteristics, particularly frequency and amplitude, are analyzed by the processor in step 74. Using an anatomical model of the outer ear as described above, the change in outer ear pressure for a particular subject using the system can be derived for a given frequency and amplitude of the audio being played. The resulting pressure from the audio, denoted as P_Music, is obtained in step 76 using the frequency and amplitude information of the audio.

[0065] The processor receives the pressure measurements P_Measured as well as the audio being played. Using timestamps, for example, the pressure waveform over time can be aligned with the audio data that was played to give the pressure waveform.

[0066] The measured pressure depends on both the baseline pressure in the ear canal (P_BL) and the pressure change due to the audio (P_Music), which can be expressed as: P_Measured = f(P_BL, P_Music) (2)

[0067] Based on empirical or experimental data, it is possible to derive a mathematical model for deriving baseline outer ear pressure (P_BL) from the pressure P_Measured measured in the presence of audio in the outer ear (with a corresponding pressure P_Music).

[0068] Thus, in step 80, a baseline outer ear pressure can be obtained based on a mathematical model that can be expressed as follows: P_BL = f(P_Measured,P_Music) (3)

[0069] The baseline outer ear pressure is obtained, for example, using a machine learning algorithm: experimental data is used for training, and standard machine learning tools such as linear regression are used to derive the relationship in equation (3).

[0070] For a linear regression model, this can be written as: P_BL=β0+β1(P_Measured)+β2(P_Music), where β0 is a constant term, and β1 and β2 are coefficients derived using experimental data.

[0071] Baseline outer ear pressure is used to detect drowsiness and / or sleep.

[0072] The state of drowsiness before sleep is characterized by frequent yawning. During yawning, pressure increases in the nasopharyngeal cavity. The middle ear is connected to the nasopharynx via the Eustachian tube. Changes in middle ear pressure result in displacement (bulging or retraction) of the tympanic membrane. In particular, during yawning, an increase in middle ear pressure results in a transient bulging of the tympanic membrane toward the outside.

[0073] As a result, in step 82, the occurrence of a yawn can be detected based on pressure changes in the outer ear baseline pressure. Measurements on a sufficiently large sample population can be used to generate a database of expected pressure changes in the outer ear during a yawn (in the presence of audio). All occurrences of a yawn detected based on pressure signal characteristics are time-stamped for further processing. In step 84, it is detected whether the frequency of yawns increases over a predetermined period of time (above a predetermined threshold). This analysis can be used to indicate a state of drowsiness in step 86.

[0074] This information is then used in step 88 to either lower the audio volume or turn the audio off completely.

[0075] Instead of, or as well as, detecting drowsiness based on yawning, pressure monitoring can also be used to detect sleep. It is known that middle ear pressure slowly increases during sleep. This increase in middle ear pressure causes the eardrum to bulge outward. This, if it creates a blocked cavity, leads to a slow increase in baseline pressure in the outer ear. Therefore, in step 89, the baseline pressure P_BL is monitored, and in step 90, it is determined whether a gradual increase in this baseline outer ear pressure is detected. If there is a gradual increase, this is used in step 92 to determine that the individual has fallen asleep, which causes the audio volume to be lowered again or the audio to be turned off entirely in step 88.

[0076] If neither drowsiness nor sleep is detected, the method returns to step 72 for the next analysis.

[0077] Figure 4 shows a plot of baseline pressure over time, illustrating a single yawn event. There are various features (labeled k-s) that can be used to enable reliable detection of yawns from pressure changes.

[0078] The in-ear speaker may further include an inertial measurement unit (IMU) that monitors head movement while listening to audio. As a person becomes drowsy, head movement is expected to decrease, eventually resulting in the head remaining stable in a particular position for an extended period of time. In this way, head movement can be correlated with pressure changes in the outer ear to detect drowsiness or sleep, and the audio can be controlled accordingly.

[0079] Additional sensing can be performed, for example, using sensors already present in the audio source, such as a cell phone, which has an IMU and other sensors such as an electroencephalography (EEG) sensor can be used to sense drowsiness or sleep.

[0080] The system can further detect arousal from sleep, for example, based on pressure changes and IMU measurement patterns, and if an impending awakening is detected, the system plays an appropriate masking noise (such as white noise, brown noise, pink noise, etc., at a predetermined intensity) to improve sleep quality.

[0081] In another example, the in-ear speaker may have a valve to vent the space between the eardrum and the in-ear speaker to the ambient environment. When the valve is opened, the ear canal is no longer a closed space. The system may then be configured to open this connection when lowering the audio volume based on drowsiness detection. This helps reduce humidity in the ear canal and establish near-normal airflow, thus reducing the risk of infection.

[0082] The above example shows the pressure sensor as a separate component added to the in-ear speaker, however the speaker itself can be used as the pressure sensor (i.e., functioning as a microphone), e.g., with duty cycle control to alternate between pressure sensing and speaker functions.

[0083] The primary example of interest is controlling the audio delivered by in-ear speakers. However, other devices, such as lighting, heating, or other sound sources such as a television or external audio device, can be controlled based on the detection of sleep or drowsiness. The control can include level control (e.g., volume or light level) or on-off control. Thus, more generally, the invention provides a method for detecting drowsiness or sleep using a pressure cavity created by an in-ear speaker; this detected information can then be used in any desired way to control audio delivery by external devices and / or the in-ear speaker itself.

[0084] The above examples detect yawn events and / or sleep-related increases in middle ear pressure from baseline ear pressure as indicators of sleepiness, however, any suitable analysis of baseline pressure that allows information about sleep or sleepiness to be determined may be performed, and these are merely possible examples.

[0085] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0086] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0087] The computer program may be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0088] When the term "adapted to" is used in the claims or the description, the term "adapted to" is meant to be equivalent to the term "configured to." When the term "arrangement" is used in the claims or the description, the term "arrangement" is intended to be equivalent to the term "system," and vice versa.

[0089] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. 1. A method for detecting drowsiness and / or sleep in a subject, comprising: receiving, during delivery of audio to the in-ear speaker, a sensed outer ear pressure between the eardrum and the in-ear speaker from a pressure sensor forming part of the in-ear speaker; receiving audio data for the transmitted audio; deriving a baseline ear pressure over time by processing (i) the frequency and amplitude characteristics of the delivered audio obtained using the audio data, and (ii) the detected outer ear pressure to remove pressure effects of the audio being listened to from the detected outer ear pressure; detecting drowsiness and / or sleep from the derived baseline ear pressure; How to do it.

2. the processor: detecting a yawn event from the baseline ear pressure; and / or detecting an increase in middle ear pressure associated with sleep from said baseline ear pressure; The method of claim 1 further comprising:

3. the processor: detecting a correct fitting of the in-ear speaker to the ear; generating an output signal indicative of any incorrect fitting; The method of claim 1 or 2, further comprising:

4. the processor: Detecting outer ear pressure during a calibration phase and determining subject-specific pressure characteristics. The method of claim 1 , further comprising:

5. 5. The method of claim 1, wherein the step of deriving baseline ear pressure over time comprises using an analytical model of the ear canal.

6. an inertial monitoring unit detecting movement of the subject; the processor additionally detecting drowsiness and / or sleep from the detected movements; The method of any one of claims 1 to 5, further comprising:

7. 1. A method of controlling an apparatus, comprising: Detecting drowsiness and / or sleep using a method according to any one of claims 1 to 6; controlling the device in response to detecting drowsiness and / or sleep; A method having the following.

8. the device has an in-ear speaker; 8. The method of claim 7, wherein the step of controlling the device comprises adapting the volume of the audio delivered by the in-ear speaker or the on / off state of the audio delivery in response to the detection of drowsiness and / or sleep.

9. detecting an arousal from sleep; controlling the delivery of audio by the in-ear speakers to improve sleep quality; The method of claim 8 further comprising:

10. 10. The method of claim 1, further comprising the step of controlling a valve to vent a space between the eardrum and the in-ear speaker to the ambient environment in response to detection of drowsiness and / or sleep.

11. A computer program having computer program code for causing a computer to carry out a method according to any one of claims 1 to 10.

12. 1. A drowsiness and / or sleep detection system for detecting drowsiness and / or sleep in a subject, comprising: an in-ear speaker having a pressure sensor for detecting outer ear pressure between the eardrum and the in-ear speaker; a processor; wherein the processor: receiving audio data for audio to be delivered to the in-ear speakers; receiving the detected outer ear pressure from the pressure sensor; (i) processing the frequency and amplitude characteristics of the delivered audio obtained using the audio data, and (ii) the corresponding detected outer ear pressure to derive a baseline ear pressure over time by removing the pressure effect of the audio being listened to from the detected outer ear pressure; detecting drowsiness and / or sleep from the derived baseline ear pressure; A system configured to run

13. the processor: Detecting a yawn event from the baseline ear pressure; and / or Detecting sleep-related increases in middle ear pressure from the baseline ear pressure. detecting drowsiness and / or sleep by The system of claim 12 further configured to:

14. 14. An audio delivery system comprising a drowsiness and / or sleep detection system according to claim 12 or 13, wherein the processor: adapting the volume of audio emitted or the on / off state of the emission of said audio in response to said detection of drowsiness and / or sleep. An audio transmission system configured to perform the following:

15. a sensor device for detecting correct fitting of an in-ear speaker to an ear, the processor being configured to generate an output signal indicative of when there is an incorrect fit; an inertial monitoring unit, wherein the processor is configured to additionally detect drowsiness and / or sleep from detected movements; a valve for venting a space between the eardrum and the in-ear speaker to an ambient environment, the processor being configured to control the valve in response to detection of drowsiness and / or sleep; and a sensor device for detecting arousals from sleep, the processor configured to control delivery of audio to improve sleep quality in response to detecting arousals from sleep; 15. The audio distribution system of claim 14, comprising one or more of:

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