Acoustic and Vibrational Analysis of Golf Club Drivers

Open Access
Author:
Kerrian, Peter Adam
Graduate Program:
Acoustics
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
February 09, 2016
Committee Members:
  • Daniel Allen Russell, Thesis Advisor
Keywords:
  • Acoustics
  • Golf
  • Experimental Modal Analysis
  • Laser Doppler Vibrometry
  • Noise
  • Golf Drivers
Abstract:
Previous studies determined that the most influential form of feedback golfers receive when determining their perception of the quality of a particular golf driver is the impact sound. As a result, players' perceptions might not be favorable for a well performing driver because they found the radiated sound unsatisfactory. Because of the importance of the sound produced when a driver impacts a golf ball, this work attempted to correlate the radiated sound from the ball/driver impact with the vibrational mode shapes of the driver. The six drivers studied in this work consisted of both new and old models that, based on anecdotal evidence from player reviews, ranged from being annoyingly loud to muted and dull. A roving impact hammer test was used to measure the Frequency Response Functions (FRFs) of the three clubhead components: face, crown, and sole. Modal frequencies and mode shapes were extracted from the FRFs using the commercial software package STAR Modal. The first modal frequency of the sole was found around 2000 Hz which is below the "trampoline" effects of the face (~ 4500 Hz). Frequency limitations of the interaction between the impact hammer and the crown prompted Scanning Laser Doppler Vibrometry measurements to obtain operating deflection shapes for high frequency modes. Similar patterns were seen in both the mode shapes and operating deflection shapes. Recordings of the radiated impact sound were made at an outdoor driving range. In order to determine how the sound changed when the impact location was not "dead center," sound recordings were made for each of the six drivers with a minimum of two ball strikes at three impact locations on the club face: center face, off center toward the toe, and off center toward the sole. Power spectral densities were calculated from a microphone that duplicated the relative location of the ball compared to the golfer's ear. Significant changes were seen in the spectra for different impact locations as well as overall amplitude for clubs perceived as loud verses dull. The frequencies of the peaks in the sound spectra were correlated to the frequencies of the mode shapes and operating deflection shapes allowing for matching which club vibrations were responsible for the sound the club makes when impacting a golf ball. For each club, there were mode shapes with frequencies very close to the peaks in the sound spectra. The clubs perceived as loud and annoying exhibited a dominant feature in the spectrum of high amplitude pure tones in the frequency range of 2kHz - 4kHz, frequencies associated with mode shapes involving the sole and crown. In contrast, the clubs perceived as muted and dull had spectral amplitudes that were roughly two orders of magnitude lower than the other clubs. Additionally, the spectra for these clubs were not defined by any single dominant feature. As expected, the contributions of peaks associated with face plate modes changed with the impact location of the ball. Implications from this research may aid golf club manufacturers in understanding the radiated sound from future golf club designs.