## 1 Introduction  
For internal combustion engine vehicles (ICEV), active sound profiling (ASP) or active sound quality control (ASQC) approach has been used to improve engine sound quality in a cabin [1, 2]. This ASP approach combines the active noise control (ANC) [3] for canceling engine booming noises of some engine orders and the active sound enrichment (ASE) [4] for enhancing insufficient engine sounds of other engine orders to satisfy the target levels. In this study, an affordable vibration actuator and control system are considered to achieve better tracking performance of a target sound using an active control approach for passenger cars. By the way, a secondary path including such an actuator attached to a structural panel of a car showed an increased uncertainty due to its vibro-acoustic property over the frequency range of interest. This made the control performance restricted especially when such a vibration actuator on a structural panel is utilized under a pure ASP algorithm. In terms of canceling engine order noise at lower frequencies, the pure ASP algorithm can work properly even with such an actuator as the uncertainty in the secondary path is relatively small at the frequencies. However, the increased uncertainty at higher frequencies with such an actuator in the path restricts the application of the ASP control approach, especially in enhancing engine order sound. Thus, a new additive ASP approach is suggested in this study, which can provide better tracking performance by using an additional purely feedforward control. As one of the algorithms for ASP, the narrowband active noise equalization (ANE) based on the filtered-x least mean square (FxLMS) was proposed by [PERSON] and [PERSON] [5]. This algorithm can intentionally leave some residual noise or strengthen it as needed through a quality factor that can control the level of the noise selectively. If the algorithm is applied to engine sound control, the amplitude of each engine order can be adjusted uniformly regardless of engine speed. However, this algorithm would be unstable when the secondary path is significantly changed because it employs the internal model. [PERSON] and [PERSON] proposed an ASP algorithm known as the command-FxLMS, which provides more improved stability than the ANE algorithm [1]. The authors introduced a target sound, which is called the command signal, and modified the cost function to minimize the pseudo error, which is the difference between the error signal and the target sound. The command-FxLMS algorithm has been utilized for implementing ASP systems in a number of studies due to its simple structure and superior stability [6; 7; 8]. In the references of [6; 7; 8], the existing built-in door loudspeakers in their test cars were utilized as secondary actuators for the ASP implementation. However, the implementation of an ASP system using such loudspeakers in a car requires additional computational resources to run the algorithm under the real-time scheme. Since this can cause a cost burden for automakers to redesign the audio board and rewrite the software to commercialize the ASP system in their cars, a novel implementation of the ASP system that is independent of the existing audio board in a car can be considered by using an affordable approach. Hence, in this study, an electronic sound generator (ESG) [9; 10] and its dedicated control unit including a power amplifier were adopted for the ASP realization with a low cost. The ESG, which is composed of a voice-coil motor, was combined with a cowl panel of a car to generate a structure-borne sound as a secondary actuator, as can be seen from Figure 1.  
This kind of arrangement using a vibration actuator and a structure in a car was used to implement an ANC system for suppressing engine order noise in a study by [PERSON] [11], and it was also applied to realize an ASE system for enriching poor order  
Figure 1: Block diagram of the pure ASP control algorithm based on the command-FxLMS. sound independently from the ANC system [11].