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Types of personalised sound technologies 
Different personalised sound technologies use different scientific principles to customise sound and can be categorised according to two main parameters:
- subjective measurement vs. objective measurement
- accounting for a subset of the listener's hearing or their environment vs. accounting for the listener's full hearing system.
Subjective tests, which are a part and parcel of every clinical Audiometry procedure specifically used to determine a person's hearing, require the listener to give feedback based on what they perceive. A common type of subjective hearing test requires the user to push a button if they can hear a tone that is played at a particular frequency and amplitude.
On the other hand, objective measurements automatically measure one or more feedback signals and do not require any input from the user.
Some personalised sound technologies measure a subset of the user's hearing, such as the acoustics of the user's outer ear (primarily the ear canal), whereas other technologies offer a full hearing measurement (measuring hearing through the outer, middle and inner ear).
Subjective, full hearing measurement
Historically, hearing aids were used to enable people with hearing loss to understand speech better by measuring their hearing and adjusting devices based on an Audiogram. However, recent developments in the field are enabling listeners with even mild to moderate hearing loss, who do not necessarily need hearing aids, to substantially improve their enjoyment of music and sound, in addition to better speech recognition. The OTC hearing Aid act is a reflection of these developments and is poised to substantially transform this field.
Other examples of products that offer subjective personalised sound are headphones by EVEN and Audeara, which provides a subjective hearing tests that take between 90 seconds and 15 minutes to complete and the Aumeo Headphone Personaliser dongle that can be connected to most media players and provides a two-minute subjective hearing test. The Mimi mobile app allows the user to undergo a six-minute subjective hearing test and the app then adjusts the mobile device's audio output based on the test results.
Objective, full hearing measurement 
The Nuraphone by Nura and are the only available consumer product that performs an objective measurement of the listener's full hearing system in order to enhance the music listening experience, primarily targeting listeners with normal hearing. The Nuraphone's proprietary technology automatically monitors otoacoustic emissions to measure the user's hearing in 1–2 minutes. The Nuraphone adapts its frequency response based on the user's hearing, allowing the user to hear more detail when listening to music.
Objective, subset hearing measurement
The Sonos Play:5 smart speaker personalises sound based on the acoustics of the room where the speaker is placed. The Sonos Play:5 measures the room's acoustics by playing testing tones, while the user's phone detects how these tones sound, and the speaker's EQ is adjusted.
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