These curves, in your example, never intersect. As I zoom in, I see that. I was looking for the point where BRA1 was less than BRA11 but it never happens so they don't intersect. To find the range of intersection, I was going to look for the change point of where one increases over the other but that just doesn't happen in this example.
library(tidyverse)
datin <- tribble(
~Row, ~Hz, ~BRA1, ~BRA11,
1, 0.03, 12.74, 12.25,
2, 0.05, 18.65, 15.73,
3, 0.07, 22.05, 17.86,
4, 0.10, 26.71, 19.92,
5, 0.20, 35.20, 24.65,
6, 0.50, 50.46, 31.19,
7, 1.00, 64.68, 36.31,
8, 1.13, 67.32, 37.20,
9, 5.00, 105.98, 46.88,
10, 10.00, 126.71, 50.64,
11, 15.00, 139.62, 52.48,
12, 20.00, 149.33, 53.90,
13, 33.00, 164.31, 55.88)
dat <- datin %>%
select(-Row) %>%
pivot_longer(cols=starts_with("BRA"))
dat %>%
filter(Hz<=.07) %>%
ggplot(aes(x=Hz, y=value, group=name, colour=name)) +
geom_point()+
geom_line()

Created on 2020-02-04 by the reprex package (v0.3.0)