A method for estimating an identity of a user of a computing system (100, 210), the method comprising: an act of estimating environment-specific alterations of a received user sound that is received at the computing system (100, 210), the environment-specific alterations being associated with an environment in which the computing system (100, 210) is placed and representing alterations that occur between a time that the user sound originated from a user and the time that the user sound was received by a microphone of the computing system (100, 210) and dependent upon one or more of a relative position between the user and the microphone of the computing system (100, 210); echoes, filtering, absorption, reflections, and/or impulse response resulting from the environment in which the microphone of the computing system is placed; and/or congestion of the room with other users, humidity, and/or detected obstacles; an act of facilitating a formulation of an expected audio model of a user's sound when a corresponding user-dependent audio model (232, 233, 234) is subject to the estimated environment-specific alterations; an act of obtaining a comparison result of comparing the received user sound with the formulation of the expected audio model; and an act of estimating whether the user corresponding to the user-dependent audio model (232, 233, 234) is the same as the user that emitted the user sound based on the comparison result, the user-dependent audio model (232, 233, 234) being stored in a multi-system store accessible such that the method may be performed for a given user across multiple systems and on a system (100, 210) that the user has never before trained to recognize the user. an act of estimating environment-specific alterations of a received user sound that is received at the computing system (100, 210), the environment-specific alterations being associated with an environment in which the computing system (100, 210) is placed and representing alterations that occur between a time that the user sound originated from a user and the time that the user sound was received by a microphone of the computing system (100, 210) and dependent upon one or more of a relative position between the user and the microphone of the computing system (100, 210); echoes, filtering, absorption, reflections, and/or impulse response resulting from the environment in which the microphone of the computing system is placed; and/or congestion of the room with other users, humidity, and/or detected obstacles; an act of facilitating a formulation of an expected audio model of a user's sound when a corresponding user-dependent audio model (232, 233, 234) is subject to the estimated environment-specific alterations; an act of obtaining a comparison result of comparing the received user sound with the formulation of the expected audio model; and an act of estimating whether the user corresponding to the user-dependent audio model (232, 233, 234) is the same as the user that emitted the user sound based on the comparison result, the user-dependent audio model (232, 233, 234) being stored in a multi-system store accessible such that the method may be performed for a given user across multiple systems and on a system (100, 210) that the user has never before trained to recognize the user.