# Meshing Stiffness--A Parameter Affecting the Emission of Gearboxes
## 1 Introduction  
The negative impact of traffic noise (and protection against it) is becoming more serious worldwide. Traffic noise is a disturbing phenomenon. A direct connection between the total helplessness of the inhabitants and the noise conditions of their dwellings has been statistically proven. Noise emissions from a car affect not only the surrounding environment, but also the people inside the car [1]. According to the law of the National Council of the Slovak Republic, the permitted noise level of cars is 74 dB. Designers must ensure that, while maintaining the car's increased performance with reduced emissions and fuel consumption, the noise level falls below the given limit [2]. At the same time, it is necessary to abide by the noise limits according to the EEC (European Economic Commission) regulation no. 51, which focuses on the homologation conditions for granting approval for external noise.  
Increased legislative pressure puts the ecological aspect of automobile noise at the forefront. This leads to the requirement of identifying and quantifying noise sources. A significant share of automobile noise is created by the vehicles' transmissions. Designers are trying to eliminate and reduce noise to a minimum, as the lower the noise, the more pleasant the car ride is. In some positive cases, such an effort also results in an increase in engine power and a reduction in fuel consumption, but the most important factor is the reduction in noise emissions.  
The gearbox in automobiles is used to transform the power generated from the engine. It can be regarded as a self-excited vibration source [3], which then affects the performance of the entire vehicle. Generally, the gearbox consists of parts like gears, shafts, bearings, synchronizers and housings, which help the gears play a significant part in the process of transmitting power. Gear transmissionerror is the main source of noise and vibration in gear transmissions, which has been proven by several researchers [4; 5; 6]. Transmission error is defined as the deviation between the theoretical position and the actual position of the output shaft, given the gear drive is perfectly accurate and stiff [7]. However, manufacturing errors and teeth deformations make transmission errors in gear transmissions unavoidable. Current research mainly aims at devising ways to measure transmission error for single-gear drives [8; 9]. With the ongoing development of the Finite Element Method and the Boundary Element Method, the technology of vibration and noise prediction of gear transmission has been rapidly improving. [PERSON] and [PERSON] based their research on these design parameters using CAE (Computer-Aided Engineering) software to predict the vibration and noise of the transmission [10]. With the aid of Finite Element Analysis, [PERSON] and [PERSON] came to the conclusion that the transmission's mechanical properties are directly related to the natural frequency and vibration [11]. Then, they continued their research work on optimizing the number of connecting bolts using Response Surface Methodology and Finite Element Analysis. RSM was used for parametric optimization, and FEA was used for calculating the modal frequency and mode shapes [12].  
In general, the gearbox is an acoustically closed system from which noise is spread mainly by vibrations of the housing surface or connected units, including the basic structure. The most important cause of noise is considered to be transmission error, which is related to meshing stiffness [13] and gear kinematic accuracy. These studies have addressed the issue of meshing stiffness [14; 15; 16]. This article deals with the impact of individual parameters on the stiffness of gearing as a source of noise and vibration in gearing. The meshing stiffness of the gearing was determined on the deformation basis of the gearing, as solved by the Finite Element Method.