A sound producing apparatus for a portable device, comprising: a speaker, for producing an audible sound; a feedback unit (15, 25), coupled to the speaker, for generating a first detected parameter indicating a detected excursion of the speaker; a signal conditioning unit, coupled to the feedback unit, which is operative to: receive from the feedback unit a parameter representing information with respect to a resonant frequency for the speaker; filter an audio input signal according to a characteristic of inverse compensation, wherein the characteristic of inverse compensation indicates a transfer function (H F) based on an inverse of a transfer function of excursion for the speaker having the resonant frequency for the speaker; output a first audio signal based on the filtered audio input signal, wherein the characteristic of inverse compensation has a minimum corresponding to the resonant frequency for the speaker, and the first audio signal has more headroom in terms of bits than that of the audio input signal; modify the transfer function (H F) indicating the characteristic of inverse compensation using the parameter representing information with respect to the resonant frequency for the speaker; and reduce the audio input signal to output the first audio signal; a compensation unit (11, 21), for generating a second audio signal based on the first audio signal, wherein the compensation unit comprises a buffer for delaying the first audio signal for looking ahead, wherein the second audio signal is generated selectively by compensation according to the first detected parameter; and a gain unit (13, 23), coupled to the compensation unit (11, 21) and the feedback unit (15, 25), for determining a gain value (Gc) according to the first detected parameter and generating a third audio signal based on the second audio signal according to the gain value (Gc). a speaker, for producing an audible sound; a feedback unit (15, 25), coupled to the speaker, for generating a first detected parameter indicating a detected excursion of the speaker; a signal conditioning unit, coupled to the feedback unit, which is operative to: receive from the feedback unit a parameter representing information with respect to a resonant frequency for the speaker; filter an audio input signal according to a characteristic of inverse compensation, wherein the characteristic of inverse compensation indicates a transfer function (H F) based on an inverse of a transfer function of excursion for the speaker having the resonant frequency for the speaker; output a first audio signal based on the filtered audio input signal, wherein the characteristic of inverse compensation has a minimum corresponding to the resonant frequency for the speaker, and the first audio signal has more headroom in terms of bits than that of the audio input signal; modify the transfer function (H F) indicating the characteristic of inverse compensation using the parameter representing information with respect to the resonant frequency for the speaker; and reduce the audio input signal to output the first audio signal; receive from the feedback unit a parameter representing information with respect to a resonant frequency for the speaker; filter an audio input signal according to a characteristic of inverse compensation, wherein the characteristic of inverse compensation indicates a transfer function (H F) based on an inverse of a transfer function of excursion for the speaker having the resonant frequency for the speaker; output a first audio signal based on the filtered audio input signal, wherein the characteristic of inverse compensation has a minimum corresponding to the resonant frequency for the speaker, and the first audio signal has more headroom in terms of bits than that of the audio input signal; modify the transfer function (H F) indicating the characteristic of inverse compensation using the parameter representing information with respect to the resonant frequency for the speaker; and reduce the audio input signal to output the first audio signal; a compensation unit (11, 21), for generating a second audio signal based on the first audio signal, wherein the compensation unit comprises a buffer for delaying the first audio signal for looking ahead, wherein the second audio signal is generated selectively by compensation according to the first detected parameter; and a gain unit (13, 23), coupled to the compensation unit (11, 21) and the feedback unit (15, 25), for determining a gain value (Gc) according to the first detected parameter and generating a third audio signal based on the second audio signal according to the gain value (Gc).