The sound pressure level in the songs of several individuals of six Acrocephalus species was measured in the natural environment and recorded on tape for various acoustic analyses. Sound propagation experiments carried out in spring and summer reed and urtica beds as well as grasslands were compared to measurements in a 'free' sound situation. Their purpose was to measure the attenuation of a sine wave of continuously increasing frequency and of played-back warbler songs over a certain distance. Further, they were to show a possible adaptiveness of the songs to the acoustic properties of the habitat as regards their frequency spectra. Additionally, vibration measurements on plant stalks were carried out, which revealed a correspondence of favourably used song frequencies with resonance optima of the plant stalks.