A method for non-mechanical-contact measuring a layer having a layer thickness of less than 100 nm, the method comprising: generating a light pulse adapted to interact with the layer to generate a thermal wave in a gas medium present adjacent the layer, thereby causing an acoustic signal to be generated; and detecting a first signal responsive to the acoustic signal by a detector without mechanically contacting the layer, wherein said first signal is representative of the measured layer, and wherein the method further comprises: improving a signal to noise ratio of the first signal to form a second signal; calculating a distance between the detector and a region of the gas medium generating the thermal wave in accordance with a speed of the acoustic signal in the gas medium multiplied by a time of flight of the acoustic signal; compensating the second signal in accordance with the calculated distance and a hyperbolic fit to a function of acoustic pressure amplitude versus detector to sample layer distance that has been established by a previous calibration process to produce a third signal that is substantially independent of a fluctuation of the distance; and determining a film characteristic of the layer based on a measurement responsive to a composition and thickness of the layer in accordance with an amplitude of the third signal in combination with a predetermined look-up table or a calculated calibration model, wherein the look-up table or the calculated calibration model has been established by a further previous calibration. generating a light pulse adapted to interact with the layer to generate a thermal wave in a gas medium present adjacent the layer, thereby causing an acoustic signal to be generated; and detecting a first signal responsive to the acoustic signal by a detector without mechanically contacting the layer, wherein said first signal is representative of the measured layer, and wherein the method further comprises: improving a signal to noise ratio of the first signal to form a second signal; calculating a distance between the detector and a region of the gas medium generating the thermal wave in accordance with a speed of the acoustic signal in the gas medium multiplied by a time of flight of the acoustic signal; compensating the second signal in accordance with the calculated distance and a hyperbolic fit to a function of acoustic pressure amplitude versus detector to sample layer distance that has been established by a previous calibration process to produce a third signal that is substantially independent of a fluctuation of the distance; and determining a film characteristic of the layer based on a measurement responsive to a composition and thickness of the layer in accordance with an amplitude of the third signal in combination with a predetermined look-up table or a calculated calibration model, wherein the look-up table or the calculated calibration model has been established by a further previous calibration. improving a signal to noise ratio of the first signal to form a second signal; calculating a distance between the detector and a region of the gas medium generating the thermal wave in accordance with a speed of the acoustic signal in the gas medium multiplied by a time of flight of the acoustic signal; compensating the second signal in accordance with the calculated distance and a hyperbolic fit to a function of acoustic pressure amplitude versus detector to sample layer distance that has been established by a previous calibration process to produce a third signal that is substantially independent of a fluctuation of the distance; and determining a film characteristic of the layer based on a measurement responsive to a composition and thickness of the layer in accordance with an amplitude of the third signal in combination with a predetermined look-up table or a calculated calibration model, wherein the look-up table or the calculated calibration model has been established by a further previous calibration.