A reason could be that conventional vibroacoustic devices require a considerable size and weight to transmit enough vibrations to a user’s body to be effective because they use inertial forces to drive a user’s body.
Now, Yusuke Yamazaki and Shoichi Hasegawa at the Tokyo Institute of Technology have invented a new mechanism for vibroacoustic device, which uses tension forces to transmit vibrations.

The device consists of two motors and a string and can transmit strong and high fidelity acoustic vibrations to a user’s body. The motors generate vibrations up to 600Hz and the string transmits this vibration. The researchers “believe this device has potential to become a new standard tool for music appreciation”.
User tests showed that the proposed device transmits vibrations to wider areas and gives better subjective impressions than conventional vibro-tactile devices.