Construction and calibration of an impact hammer

Waltham, Chris; Kotlicki, A.

doi:10.1119/1.3177062

Cited by 7 publications

(5 citation statements)

References 5 publications

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“…The force was calibrated by making the same measurement, in air, with an impact hammer. 15 In the case of the guitar, the modes were observed at the same frequencies by both methods so calibration was straightforward. For the violin, small shifts were seen in modal frequencies as a result of the shaker mass, but the modes were still identifiable.…”

Section: Admittance Measurementsmentioning

confidence: 98%

Vibrational behavior of a soundbox in an atmosphere with a variable speed of sound

Chen

Kotlicki

Waltham

et al. 2012

The Journal of the Acoustical Society of America

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This paper describes a semi-quantitative method, suitable for a student laboratory exercise that shows that the acoustic properties of the soundbox of a musical instrument depend on the sound speed of the atmosphere surrounding and filling the instrument. A gas tent was constructed and used to enclose instruments in helium, carbon dioxide and mixtures thereof, allowing the sound speed to be varied from 250 to 1000 m/s. Soundboard admittance data were taken using a guitar and a violin as examples. The data, expressed as contour plots, show clearly the qualitative relationship between air and wood modes, and the guitar data are compared with a simple mechanical model. Experimental details of the construction and operation of gas tent are given, with attention paid to safety issues.

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Section: Admittance Measurementsmentioning

confidence: 98%

Vibrational behavior of a soundbox in an atmosphere with a variable speed of sound

Chen

Kotlicki

Waltham

et al. 2012

The Journal of the Acoustical Society of America

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“…The TFS were embedded into a treadmill-installed force platform (DBCEEWI, AMTI, USA). The impact hammer has been calibrated using a known mass and accelerometer (Waltham & Kotlicki, 2009) and connected to a 2 channel charge amplifier (Rion, UV-16). The devices were synchronized using Nexus data acquisition system (Oxford Metrics Ltd, Oxford, UK) at a sample frequency of 2000 Hz.…”

Section: Measurementmentioning

confidence: 99%

Evaluating dynamic error of a treadmill and the effect on measured kinetic gait parameters: Implications and possible solutions

Garofolini

Taylor

Lépine

2019

Journal of Biomechanics

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The dynamic properties of instrumented treadmills influence the force measurement of the embedded force platform. We investigated these properties using a frequency response function, which evaluates the ratio between the measured and applied forces in the frequency domain. For comparison, the procedure was also performed on the gold-standard ground-embedded force platform. A predictive model of the systematic error of both types of force platform was then developed and tested against different input signals that represent three types of running patterns. Results show that the treadmill structure distorts the measured force signal. We then modified this structure with a simple stiffening frame in an attempt to reduce measurement error. Consequently, the overall absolute error was reduced (-22%), and the error in force-derived metrics was also sufficiently reduced:-68% for average loading rate error and-80% for impact peak error. Our procedure shows how to measure, predict, and reduce systematic dynamic error associated with treadmill-installed force platforms. We suggest this procedure should be implemented to appraise data quality, and frequency response function values should be included in research reports.

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“…18͒ amplifier unit whose two outputs were proportional to acoustic pressure and velocity. The soundboard was excited by an impact hammer 19 striking the string-bar at normal incidence. All four signals ͑hammer, accelerometer, acoustic pressure and velocity͒ were fed into a Measurement Computing 1208FS ͑Ref.…”

Section: Measurementsmentioning

confidence: 99%

Vibro-acoustic characteristics of an Aoyama Amphion concert harp

Daltrop

Kotlicki

Waltham

2010

The Journal of the Acoustical Society of America

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The mechanical admittance of the soundboards of four full-size concert harps from three manufacturers was measured, and the results show that there is little variation between them. More detailed vibro-acoustic data were then obtained for an Aoyama Amphion harp. Analysis of these data show that the individual soundholes amplify the radiated sound in successive frequency bands associated with the modal frequencies of the soundboard. The lower holes tend to contribute at the lower end of the frequency scale, and the higher holes at the higher end of the scale.

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Construction and calibration of an impact hammer

Cited by 7 publications

References 5 publications

Vibrational behavior of a soundbox in an atmosphere with a variable speed of sound

Vibrational behavior of a soundbox in an atmosphere with a variable speed of sound

Evaluating dynamic error of a treadmill and the effect on measured kinetic gait parameters: Implications and possible solutions

Vibro-acoustic characteristics of an Aoyama Amphion concert harp

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