1. Graduate Research Assistant, Structural Dynamics and Acoustic Systems Laboratory, Univ. of Massachusetts Lowell, One University Ave., Lowell, MA 01854.
2. Graduate Research Assistant, Structural Dynamics and Acoustic Systems Laboratory, Univ. of Massachusetts Lowell, One University Ave., Lowell, MA 01854 (corresponding author).
3. Professor, Structural Dynamics and Acoustic Systems Laboratory, Univ. of Massachusetts Lowell, One University Ave., Lowell, MA 01854.