Optimization of Shunted Loudspeaker for Sound Absorption by Fully Exhaustive and Backtracking Algorithm

Zihao Li,Xin Li,Bilong Liu

doi:10.3390/app11125574

Abstract

The shunted loudspeaker with a negative impedance converter is a physical system with multiple influencing parameters. In this paper, a fully exhaustive backtracking algorithm was used to optimize these parameters, such as moving mass, total stiffness, damping, coil inductance, force factor, circuit resistance, inductance and capacitance, in order to obtain the best sound absorption in a specific frequency range. Taking the maximum average sound absorption coefficient in the range of 100–450 Hz as the objective function, the optimized parameters of the shunted loudspeaker were analyzed. Simulation results indicated that the force factor and moving mass can be sufficiently reduced in comparison with that of a typical four-inch loudspeaker available on the market. For a given loudspeaker from the market as an example, the four optimized parameters of the shunted loudspeaker were given, and the sound absorption coefficient was measured for verification. The measured results were in good agreement with the predicted results, demonstrating the applicability of the algorithm.

Highlights

Low-frequency sound absorption within a limited space is always a challenge in noise control engineering
For an shunted loudspeaker (SL) with a negative impedance converter (NIC), the circuit parameters, such as resistance, capacitance and inductance, are transformed due to the negative impedance converter. This can effectively adjust the acoustic impedance of the coupled system to match that of the air in a wide frequency range [1]
The results revealed that the total stiffness was smaller than that of a typical SL reported in the literature

Summary

Introduction

Low-frequency sound absorption within a limited space is always a challenge in noise control engineering. For an SL with a negative impedance converter (NIC), the circuit parameters, such as resistance, capacitance and inductance, are transformed due to the negative impedance converter. This can effectively adjust the acoustic impedance of the coupled system to match that of the air in a wide frequency range [1]. Good sound absorption for low frequencies can be achieved in a relatively narrow frequency band. In their later research, analogous analysis, experimental optimization of the SL and active control theory were carried out. Due to the low-frequency sound absorption properties of the SL, many structures relevant to the SL that have better sound absorption performance have been reported [7,8,9,10]

Results

Discussion

Conclusion