Acoustic waves are characterized by their frequency (cycles per second), wavelength (distance between cycles) and amplitude (height of the wave). Depending on the frequency of the waveform, sound waves can be classified as infrasonic, sonic and ultrasonic. Sonic waves have frequencies between 20 and 20,000 Hz, which correspond to the frequency range of human hearing. Waves with frequencies below 20 Hz are classified as infrasonic, while waves with frequencies above 20,000 Hz are classified as ultrasonic.”1
The use of ultrasonic acoustic waves and their effect on the drying and film performance of industrial inline coatings is supported by a broad and growing body of research. Over the past decade, commercial acceptance of ultrasonic acoustically assisted (USAA) heat and mass transfer drying has grown rapidly in consumer product inline converting applications such as printing and adhesive lamination. USAA drying provides energy cost savings, increased throughput and reduced footprint. It has also proven to be a unique fit for niche applications, such as cold seal adhesives in which drying completeness is critical for tack. Although USAA drying has been successfully evaluated as an energy-efficient drying method for certain high free-moisture-content wood species, the relationship between waterborne coatings, wood substrates and USAA drying remains uncharted.