A Quality Design of Bone Conduction Voice in Magnetic Resonance Imaging Noise

The acoustical driving noise of Magnetic Resonance Imaging (MRI) device is loud. The bone conduction microphone is used to transmit the subject's voice. It is better than other microphones in the MRI examination. When the subject becomes unwell, the doctor cannot understand the transmitted voice of subject. Because the voice is small and the MRI acoustical noise is loud. Here, the MRI acoustical noise generates the vibration to the subject's body. The vibration propagates to the microphone and deteriorates the communication quality.The purpose is to clarify the relation between the shielding area of the bone conduction microphone and the communication quality. We propose the theoretical formula of the characteristic of the vibration propagation and the ratio of the vibration acceleration to the sound pressure based on the distributed constant circuit. The communication quality in the case of the shielding the bone conduction microphone was verified using the theoretical formula. The estimated communication quality was equal to the experimental communication quality with high accuracy. In the result, it was shown that the communication quality was improved by the shielding area such as the earmuff to quality that the doctor can recognize the subject's small voice.