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Apparent mass of small children: experimental measurements
1Department of Mechanical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK. j.a.giacomin@sheffield.ac.uk
Insights
Researchers developed a new method to measure whole-body vibration in children under 18kg. The study found children
Area of Science:
- Biomechanics
- Human Factors Engineering
- Pediatric Ergonomics
Background:
- Assessing whole-body vibration (WBV) exposure is crucial for understanding potential health impacts.
- Existing WBV measurement protocols are primarily designed for adults, lacking specific methodologies for young children.
- Understanding pediatric WBV response is essential for designing safe environments and equipment for children.
Purpose of the Study:
- To develop and validate a testing facility and protocol for measuring seated, vertical WBV response in small children (<18 kg).
- To characterize the apparent mass and phase of children within a specific frequency range (1-45 Hz).
- To compare pediatric WBV response data with existing data for primates and adult humans.
Main Methods:
- A specialized test facility and protocol were created, adhering to BS7085 human vibration testing guidelines and ethical standards for research with children.
- Eight children participated, tested at vibration amplitudes of 0.8 and 1.2 m/s² using band-limited, Gaussian, white noise signals (1-50 Hz).
- Driving point apparent mass modulus and phase curves were determined, incorporating parental involvement and child comfort measures.
Main Results:
- All children exhibited a single, principal anti-resonance in their vibration response.
- The mean frequency of the apparent mass peak for children was 6.25 Hz, closely aligning with data for small primates (6.5-8.5 Hz) and adults with backrest support (6.5-8.6 Hz).
- The peak mean normalized apparent mass for children was 1.54, comparable to values reported for small primates (1.19-1.45) and adults with backrest support (1.28).
Conclusions:
- The developed facility and protocol effectively measure WBV response in small children, providing valuable data for pediatric ergonomics.
- Pediatric WBV response characteristics, particularly the apparent mass peak frequency and magnitude, are similar to those of primates and adults with backrest support.
- The findings highlight significant differences compared to ISO standard 5982 for adults without backrest support, emphasizing the need for child-specific vibration assessment.
Abstract:
A test facility and protocol were developed for measuring the seated, vertical, whole-body vibration response of small children of less than 18 kg in mass over the frequency range from 1 to 45 Hz. The facility and protocol adhered to the human vibration testing guidelines of BS7085 and to current codes of ethics for research involving children. Additional procedures were also developed which are not currently defined in the guidelines, including the integral involvement of the parents and steps taken to maximize child happiness. Eight children were tested at amplitudes of 0.8 and 1.2 m/s(2) using band-limited, Gaussian, white noise acceleration signals defined over the frequency interval from 1 to 50 Hz. Driving point apparent mass modulus and phase curves were determined for all eight children at both test amplitudes. All results presented a single, principal, anti-resonance, and were similar to data reported for primates and for adult humans seated in an automotive posture which provided backrest support. The mean frequency of the apparent mass peak was 6.25 Hz for the small children, as compared to values between 6.5 - 8.5 Hz for small primates and values between 6.5 - 8.6 Hz for adults seated with backrest support. The peak value of the mean, normalized, apparent mass was 1.54 for the children, which compares to values from 1.19 to 1.45 reported in the literature for small primates and 1.28 for adults seated with backrest support. ISO standard 5982, which specifies a mean, normalized, apparent mass modulus peak of 1.50 at a frequency of 4.0 Hz for adults seated without backrest support, provides significant differences.
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