Estudo da geração de infrassom com diferentes tipos de transdutores

Abstract

A characteristic of infrasound is the induction of vibratory sensation. In this study, the sound pressure level at very low frequencies necessary to produce a vibratory sensation on a person was investigated. For this, measurements were made to see the relation between the sound pressure level generated by a test signal and the induced acceleration levels at a test person’s body. It was found that the resulting acceleration level is 10 dB less than a test signal’s sound pressure level. Based on measurements of another research, that determined the body’s acceleration necessary to produce a vibratory sensation, it was found that a sound pressure level of about 100dB at infrasound frequencies is needed to ensure a vibratory sensation. After that, different transducer principles for generating infrasound frequencies at those levels were studied, and it was proved that the transducer principles already present in the market are not suitable for the infrasound generation. Some alternative transducer principles were studied, such as the Organ Pipe transducer, or the Rotary Woofer, but also proved too big and expensive for a real infrasound generation application. Therefore, new transducer principles were studied, and it was found that the airflow modulation principle was the best option to generate infrasound. A prototype of a transducer with this principle was built, and the measurements results revealed that the airflow modulation principle generates not only infrasound frequencies, but a high impulse, with a wide range of frequencies. Some optimizations for the project continuation were suggested, making the airflow modulation principle a promising transducer principle for infrasound generation, necessary to produce a vibratory nsensation which positively influences the music experience.