title: An ultrasound personal locator for time-activity assessment.
abstract: The UC Berkeley Time-Activity Monitoring System (UCB-TAMS) was developed to measure time-activity in exposure studies. The system consists of small, light, inexpensive battery-operated 40-kHz ultrasound transmitters (tags) worn by participants and an ultrasound receiver (locator) attached to a datalogger fixed in an indoor location. Presence or absence of participants is monitored by distinguishing the unique ultrasound ID of each tag. Efficacy tests in rural households of highland Guatemala showed the system to be comparable to the gold-standard time-activity measure of direct observation by researchers, with an accuracy of predicting time-weighted averages of 90-95%, minute-by-minute accuracy of 80-85%, and sensitivity/specificity values of 86-89%/71-74% for one-minute readings on children 3-8 years-old. Additional controlled tests in modern buildings and in rural Guatemalan homes confirmed the performance of the system with the presence of other ultrasound sources, with multiple tags, covered by clothing, and in other non-ideal circumstances.
authors.affiliation: Received from: EME Systems, Berkeley, CA, USA.
authors.forename: Gian
authors.initials: G
authors.lastname: Allen-Piccolo
authors.forename: Jamesine V
authors.initials: JV
authors.lastname: Rogers
authors.forename: Rufus
authors.initials: R
authors.lastname: Edwards
authors.forename: Michael C
authors.initials: MC
authors.lastname: Clark
authors.forename: T Tracy
authors.initials: TT
authors.lastname: Allen
authors.forename: Ilse
authors.initials: I
authors.lastname: Ruiz-Mercado
authors.forename: Kyra N
authors.initials: KN
authors.lastname: Shields
authors.forename: Eduardo
authors.initials: E
authors.lastname: Canuz
authors.forename: Kirk R
authors.initials: KR
authors.lastname: Smith
mesh_terms: D016902:Air Pollution, Indoor; D002648:Child; D002675:Child, Preschool; D004781:Environmental Exposure; D004784:Environmental Monitoring / Q000295:instrumentation* / Q000379:methods; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008297:Male; D011159:Population Surveillance / Q000379:methods; D013647:Task Performance and Analysis; D014465:Ultrasonics