A photo-acoustic conversion based sound emitter device, comprising - a sound output surface for transmitting sound wave vibrations to a medium outside the device; - an optical waveguide, configured to transmit light through an optical path within the device; - a first and second photo-acoustic conversion volumes, at different distances from the sound output surface, for transmitting sound generated in the first and second volume to the medium via the sound output surface, the optical path extending directly or indirectly successively through the first and second photo-acoustic conversion volume, wherein - the device comprises an intermediate volume separating the first and second photo-acoustic conversion volumes along the optical path, the intermediate volume having a lower light absorption coefficient than the first and second photo-acoustic conversion volumes; and/or - the first and second photo-acoustic conversion volume have a different cross-section area size and/or shape with virtual planes perpendicular to the optical path; and/or - the first and second photo-acoustic conversion volumes have different optical absorption coefficients, or a different optical wavelength dependence of these optical absorption coefficients; wherein the device further comprises: - a substrate, the optical waveguide being integrated on a surface of the substrate; the device being characterized in that - the first photo-acoustic conversion volume is formed by a first layer of or part of a first layer on or in the substrate, with a surface of the first layer extending in parallel with the surface of the substrate, overlying or underlying the optical waveguide; - the second photo-acoustic conversion volume is formed by a second layer of or part of a second layer over the first layer, a surface of the second layer extending in parallel with the surface of the substrate, overlying or underlying the optical waveguide; and in that the device further comprises - an optical coupling structure located underneath or above said first and second layers, coupled to the optical waveguide, configured to redirect light traveling in the optical waveguide through said layers in a direction transverse to the surface of the substrate. - a sound output surface for transmitting sound wave vibrations to a medium outside the device; - an optical waveguide, configured to transmit light through an optical path within the device; - a first and second photo-acoustic conversion volumes, at different distances from the sound output surface, for transmitting sound generated in the first and second volume to the medium via the sound output surface, the optical path extending directly or indirectly successively through the first and second photo-acoustic conversion volume, wherein - the device comprises an intermediate volume separating the first and second photo-acoustic conversion volumes along the optical path, the intermediate volume having a lower light absorption coefficient than the first and second photo-acoustic conversion volumes; and/or - the first and second photo-acoustic conversion volume have a different cross-section area size and/or shape with virtual planes perpendicular to the optical path; and/or - the first and second photo-acoustic conversion volumes have different optical absorption coefficients, or a different optical wavelength dependence of these optical absorption coefficients; - the device comprises an intermediate volume separating the first and second photo-acoustic conversion volumes along the optical path, the intermediate volume having a lower light absorption coefficient than the first and second photo-acoustic conversion volumes; and/or - the first and second photo-acoustic conversion volume have a different cross-section area size and/or shape with virtual planes perpendicular to the optical path; and/or - the first and second photo-acoustic conversion volumes have different optical absorption coefficients, or a different optical wavelength dependence of these optical absorption coefficients; - the first and second photo-acoustic conversion volumes have different optical absorption coefficients, or a different optical wavelength dependence of these optical absorption coefficients; - a substrate, the optical waveguide being integrated on a surface of the substrate; the device being characterized in that - the first photo-acoustic conversion volume is formed by a first layer of or part of a first layer on or in the substrate, with a surface of the first layer extending in parallel with the surface of the substrate, overlying or underlying the optical waveguide; - the second photo-acoustic conversion volume is formed by a second layer of or part of a second layer over the first layer, a surface of the second layer extending in parallel with the surface of the substrate, overlying or underlying the optical waveguide; and in that the device further comprises - an optical coupling structure located underneath or above said first and second layers, coupled to the optical waveguide, configured to redirect light traveling in the optical waveguide through said layers in a direction transverse to the surface of the substrate.