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GENERAL INFORMATION
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Title of Dataset: Low-cost measurement of facemask efficacy for filtering expelled droplets during speech

Authors: Fischer, Emma; Fischer, Martin; Grass, David; Henrion, Isaac; Warren, Warren; Westman, Eric

Funder: Duke University

Associated Publications: Science Advanced 2020. https://advances.sciencemag.org/lookup/doi/10.1126/sciadv.abd3083

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DATA & FILE OVERVIEW
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This dataset contains movie recordings from droplets passing through a light sheet. The camera recorded scattered light from particles in the laser beam before the speech (~10 s), during speech (~10 s), and for a period of droplet clearing (~20 s). The speech consisted of five repetitions of the phrase “Stay healthy, people.” We tested various masks (Set 1-12), a mask material, and 2 sets of controls with no mask.

The nomenclature of the masks during the experiment differed from the names in the manuscript (during the experiment analysis some of the masks were blinded). The set number and name in the publication corresponds to the spoken names and file names according to the table below:

Set	Name(in paper)	SpokenName	FileName
1	Surgical	Day3_Surgical	Set01/Surgical
2	N95     	Day3_N95	Set02/N95
3	Knitted 	Day3_Knitted	Set03/Knit
4	PolyProp	Day3_Polypropylene	Set04/Poly
5	Poly/Cotton	Day4_Mask5	Set05/Mask5
6	MaxAT   	Day4_Mask6	Set06/Mask6
7	Cotton2  	Day3_Cotton	Set07/Cotton
8	Cotton4 	Day4_Mask7	Set08/Mask7
9	Cotton3 	Day4_Mask1	Set09/Mask1
10	Cotton1 	Day4_Mask2	Set10/Mask2
11	Fleece  	Day3_NeckFleece	Set11/Fleece
12	Bandana 	Day3_Bandana	Set12/Bandana
13	Cotton5   	Speaker1_Cotton	Set13/Speaker1_Cotton
14	Fitted N95	Speaker1_N95fit	Set14/Speaker1_N95Fit
15	Swath   	Day4_Mask4	Set15/Mask4 (set 13 was Swath, which now is set 15)
16_1	None    	Day3_NoMask	Set14_Run1/None
16_2	None    	Day4_NoMask	Set14_Run2/None

SP1	Speaker1	(None, Surgical, Cotton, Bandana)
SP2	Speaker2	(None, Surgical, Cotton, Bandana)
SP3	Speaker3	(None, Surgical, Cotton, Bandana)
SP4	Speaker5	(None, Surgical, Cotton, Bandana)


File Format Note: The videos are in mp4 format.

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METHODOLOGICAL INFORMATION
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An operator wears a face mask and speaks into the direction of an expanded laser beam inside a dark enclosure. Droplets that propagate through the laser beam scatter light, which is recorded with a cell phone camera. The frame size was set to 1920 x 1080 pixels, the focal distance to 20 cm, the exposure time to 1/50 s, and the frame rate to 30/s. At this focal distance, each camera pixel recorded an area of 120 µm x 120 µm at the position of the light sheet. 

The code for analysis of the particle count was written in Mathematica. The source code in Notebook format is available from the corresponding author on reasonable request.