INTRODUCTION Creep groan noise is generated when a brake pedal is slowly released in an automatic transmission car which is initially stationary. Creep groan also occurs at low brake pressures, when a car is driven slowly (about 0.01 ∼ 0.05kph). Stick-slip phenomenon of friction material and disc, and the structural dynamics of a car are related to this. Stick-slip phenomenon is caused by the difference in frictional coefficient between static state and dynamic state, and this leads to momentary change in braking force. This phenomenon becomes a vibration source, and causes the vibration to the entire chassis platform and body, as well as brake, and generates noise that offends the ears of passengers. Until now, evaluation of creep groan noise has been conducted through real car test driving. In the event of a problem, the improvement of friction material was the most effective. Thus, in the early development stage, the evaluation was conducted before other tests. Meantime, it is likely that there will be a large variation in findings in accordance with temperature, humidity, and soaking time on the day of test driving. In addition, the change in creep drive torque according to engine specification and the evaluator can cause errors. This paper measured the interior noise in the event of creep groan noise, using a chassis dynamometer facilitating the control of temperature and humidity, and the drive and the brake of a car, in order to increase the reliability in evaluation. The understanding of stick-slip phenomenon was improved based on the findings about vibration, and the noise and the frequency band measured by dynamometer, and then the influence of stick-slip on creep groan was analyzed. In addition, through ODS analysis, the vibration mode in the main frequency band for creep groan noise was analyzed. The differences in the vibration and noise level about the specifications compared through the analysis of the attributes of vibration depending on the transfer path from vibration source to chassis platforms and body, and the causes of the differences were investigated. Lastly, the improvement of creep groan noise not only by friction material but also by noise reduction through the modification of the attributes of other components was sought after. Analysis of Creep Groan Behavior Evaluation with dynamometer In this paper, car's behavioral attributes in the event of noise was analyzed in order to work out a way to improve creep groan noise. In order to objectify the repeatability of reappearance and increase the reliability in the findings from an evaluation, a chassis dynamometer was used. In order to find appropriate environmental conditions for an evaluation of creep groan, the interior noise by temperature, humidity and soaking time was measured. As a result, environmental conditions were set at 10 °C which generates the highest noise level, RH 85%, and 12-hour soaking which stabilizes noise variation. 2012-01-1824 Published 09/17/2012 Copyright © 2012 SAE International doi:10.4271/2012-01-1824 saepcmech.saejournals.org Research for Brake Creep Groan Noise with Dynamometer Taeho Jung and Seung Chung Hyundai Motor Company ABSTRACT This paper deals with creep groan noise in vehicles which is a low frequency vibration problem at 20 ∼500Hz that appears in low brake pressures and extremely low speed especially in automatic transmission car, where there is a transition from static to dynamic condition. The vibration causing the noise is commonly thought to result from friction force variation between brake disc and pad in stick-slip phenomena. Simulation results are confirmed through dynamometer testing. Then presented noise contribution factor analysis by experimental approach between chassis components. CITATION: Jung, T. and Chung, S., "Research for Brake Creep Groan Noise with Dynamometer," SAE Int. J. Passeng. Cars - Mech. Syst. 5(4):2012, doi:10.4271/2012-01-1824. ____________________________________ 1224Dow