TABLE I.

Internal Site Summary Statistics: Demographic and Measurement Information

Variable	Overall		Site 1		Site 2		Site 3
	N	(%)	N	(%)	N	(%)	N	(%)
Total subjects	68	100	21	100	16	100	31	100
Gender–male	66	97	21	100	16	100	29	94
Age
<30	28	41	8	38	8	50	12	39
30–40	20	29	6	29	5	31	9	29
>40	20	29	7	33	3	19	10	32
Education
< High School (HS)	8	12	1	5	4	25	3	10
HS/GED	41	61	12	57	8	53	22	72
> HS	18	26	8	38	4	23	6	18
TradeA
Carpenter	34	50	8	38	13	81	13	42
Electrician	5	7	—	—	—	—	5	16
Ironworker	6	9	—	—	1	6	5	16
Laborer	12	18	5	7	2	13	5	16
Operating engineer	3	4	—	—	—	—	3	4
Plumber/pipefitter	8	12	8	38	—	—	—	—
Years in construction
<10 years	31	45	10	46	10	63	10	32
10–20 years	20	30	6	30	4	25	11	35
>20 years	17	25	5	24	2	13	10	32
Hearing ability
Good	36	53	10	49	10	63	16	51
Fair	28	41	10	46	4	25	14	46
Poor	4	6	1	5	2	13	1	3
Tinnitus
Never	14	21	5	22	3	19	7	21
Rarely	28	41	7	31	7	44	15	49
Sometimes	18	27	8	39	3	19	7	21
Frequently	5	8	1	6	2	13	2	6
Always	2	3	1	3	1	9	1	3
Family hearing loss: Yes	14	21	5	24	4	22	7	21
	Days		Days		Days		Days
Time between measurements	Mean	SD	Mean	SD	Mean	SD	Mean	SD
First and second	73	9	75	4	70	3	74	7
First and third	122	16	125	6	120	2	123	6

^AStatistically significant differences across sites (χ², p ≤ 0.05).