A method comprising the following steps: a) according to a first alternative, providing an acoustic resonator, the acoustic resonator comprising an absorption element having a surface portion, providing a sample fluid or a fluid mixture comprising the sample fluid such that the acoustic resonator is filled with the sample fluid or the fluid mixture comprising the sample fluid, wherein the surface portion of the absorption element is in contact with the sample fluid or the fluid mixture comprising the sample fluid, or according to a second alternative, providing an acoustic resonator, providing a fluid mixture comprising a sample fluid such that the acoustic resonator is filled with the fluid mixture, wherein the fluid mixture comprises, in addition to the sample fluid, at least one absorption fluid or one or more absorption particles, b) according to the first alternative, irradiating the surface portion of the absorption element with a first electromagnetic radiation such that the absorption element at least partially absorbs the first electromagnetic radiation in the region of the surface portion, or according to the second alternative, irradiating the fluid mixture with a first electromagnetic radiation such that the absorption fluid or the absorption particles at least partially absorb the first electromagnetic radiation, such that, in both alternatives, by way of the absorption, pressure energy is produced in the sample fluid or the fluid mixture comprising the sample fluid, wherein the first electromagnetic radiation is amplitude modulated or frequency modulated at a modulation frequency, c) measuring an acoustic response signal of the acoustic resonator generated by the absorption of the first electromagnetic radiation taking place in step b), d) determining at least one amplitude or phase (φ) of the acoustic response signal having the modulation frequency of the first electromagnetic radiation characterized in that in a further step a property of the acoustic resonator is determined, wherein one of the following steps or both followings steps is provided: e) determining a resonant frequency of the acoustic resonator from at least the amplitude or the phase (φ) determined in step d), f) determining a damping property of the acoustic resonator. a) according to a first alternative, providing an acoustic resonator, the acoustic resonator comprising an absorption element having a surface portion, providing a sample fluid or a fluid mixture comprising the sample fluid such that the acoustic resonator is filled with the sample fluid or the fluid mixture comprising the sample fluid, wherein the surface portion of the absorption element is in contact with the sample fluid or the fluid mixture comprising the sample fluid, or according to a second alternative, providing an acoustic resonator, providing a fluid mixture comprising a sample fluid such that the acoustic resonator is filled with the fluid mixture, wherein the fluid mixture comprises, in addition to the sample fluid, at least one absorption fluid or one or more absorption particles, providing a sample fluid or a fluid mixture comprising the sample fluid such that the acoustic resonator is filled with the sample fluid or the fluid mixture comprising the sample fluid, wherein the surface portion of the absorption element is in contact with the sample fluid or the fluid mixture comprising the sample fluid, or according to a second alternative, providing an acoustic resonator, providing a fluid mixture comprising a sample fluid such that the acoustic resonator is filled with the fluid mixture, wherein the fluid mixture comprises, in addition to the sample fluid, at least one absorption fluid or one or more absorption particles, b) according to the first alternative, irradiating the surface portion of the absorption element with a first electromagnetic radiation such that the absorption element at least partially absorbs the first electromagnetic radiation in the region of the surface portion, or according to the second alternative, irradiating the fluid mixture with a first electromagnetic radiation such that the absorption fluid or the absorption particles at least partially absorb the first electromagnetic radiation, such that, in both alternatives, by way of the absorption, pressure energy is produced in the sample fluid or the fluid mixture comprising the sample fluid, wherein the first electromagnetic radiation is amplitude modulated or frequency modulated at a modulation frequency, according to the second alternative, irradiating the fluid mixture with a first electromagnetic radiation such that the absorption fluid or the absorption particles at least partially absorb the first electromagnetic radiation, such that, in both alternatives, by way of the absorption, pressure energy is produced in the sample fluid or the fluid mixture comprising the sample fluid, wherein the first electromagnetic radiation is amplitude modulated or frequency modulated at a modulation frequency, c) measuring an acoustic response signal of the acoustic resonator generated by the absorption of the first electromagnetic radiation taking place in step b), d) determining at least one amplitude or phase (φ) of the acoustic response signal having the modulation frequency of the first electromagnetic radiation e) determining a resonant frequency of the acoustic resonator from at least the amplitude or the phase (φ) determined in step d), f) determining a damping property of the acoustic resonator.