Hi Silvija, I am familiar with the interesting and often loud vocalizations of lorikeets.

I do not believe it is possible to fix clipping in an audio program. If clipping is occurring, your signal has reached, and likely exceeded the maximum value. You are therefore missing information about dynamic levels above the clip threshold that you can never recover.

The recording equipment really needs to be selected specifically for your dynamic and frequency range of interest. You want to be able to turn down the amplification on the recording system such that clipping never occurs, but you still have a clear signal to capture the more quiet calls and hisses the lorikeets make. If you can find the dynamic range of the lorikeet calls, that would be a good start for selecting the right equipment and adjusting the equipment you already have.

Using a limiter and/or compressor should help decrease the loudness of the loud calls, while also increasing the loudness of the soft calls, but given the differences in their call volume, I do not think you can rely on this exclusively. This method may also interfere with your ability to analyze call dynamics.

Another thought is to consider if you actually need to worry about clipping on the loud calls. Can you still analyze the vocalizations based on frequency or pattern of calls? Are the louder calls that clip as relevant to your research as some of the more quiet calls? Your final question, "Is it okay to use fixed signals?", is really dependent on your research question.

Christopher A Varnon thank you for the answer. I think I can use clipped calls for pattern analysis and classification.

For most analyses, the biggest problem with clipped recordings is not the loss of reliable information about relative amplitude ("dynamics"); it's the corruption of the spectral content of the recording. Clipping introduces spurious energy into the recording at frequencies that are harmonics of the true signal. In some cases, sounds that are purely tonal (no harmonic content) will end up having strong harmonics in the clipped recording. Sounds that truly do have harmonics (like many parrot vocalizations) will be recorded with distorted relative powers in different harmonics. Most kinds of analysis that aim to classify sounds or measure their relative similarity (e.g., spectrogram cross-correlation, dynamic time warping, etc.) may be severely affected by such distortions.

What about "fixing" a clipped recording? Many digital audio editing programs (e.g., Audacity, Audition) include tools for "fixing" clipping. However, these tools are not intended to provide a perfect reconstruction of what the unclipped signal would have looked like. They're meant for rendering the harmonic distortions of brief periods of clipping in music or speech recordings inaudible to the human ear. This is very different from what would be needed for a quantitative measurement and classification analysis.

Although there may be some kinds of analysis that could tolerate clipping (e.g., analyses focused on temporal patterning of sounds that don't measure spectral content), in general I recommend against using clipped recordings for pattern analysis and classification. You're likely to get quite different results from what you would obtain using unclipped recordings of the same signals.

Thank you Russ Charif for detailed explanation.

While Russ Charif offered an excellent explanation of how clipped recordings can be analyzed, if you are going to be making more recordings let me suggest a few things to help avoid clipping. First, don't use automatic gain control. Second, if the signal is so strong that it clips even at minimum gain, switch to a lower sensitivity setting on your mike preamp, if it has one. Third, if all else fails, move the microphone away from the bird.