The Santa Barbara Channel Experiment (SBCX)

FFP Acoustic Data

Contained within this page are acoustic data recorded during SBCX. Three separate events are given; one short range (1.2 km) nonstationary event, and two longer range (7.1 and 15.3 km) stationary events. Refer to the A/X 2 master timesheet for additional information. Cross spectral densities for these datasets have been precomputed; they can be found here.

How to read these files

These files have been stripped of most of their original CASDE header information, to facilitate analysis. Once downloaded, each file can be loaded into MATLAB with the function read_ffp_channel.m. The format of the header is as follows:

Name	Type	Description
`byteorder`	`uint32`	Byte order test - should be 1 if ordering is correct. If not, one may need to byteswap.
`acoid`	`uint32`	Array number (1 - 5)
`cn`	`uint32`	Channel number (1 - 30)
`fs`	`double`	Sample frequency (4000 Hz)
`df`	`uint32`	Data format (32 bit integers)
`frame_start`	`uint32`	Starting frame number

`ztyd`	`uint32`	Yearday of Frame 0
`zthr`	`uint32`	Hour of Frame 0
`ztmn`	`uint32`	Minute of Frame 0
`ztss`	`uint32`	Second of Frame 0
`ztus`	`uint32`	Microsecond of Frame 0

`styd`	`uint32`	Yearday of first frame in file
`sthr`	`uint32`	Hour of first frame in file
`stmn`	`uint32`	Minute of first frame in file
`stss`	`uint32`	Second of first frame in file
`stus`	`uint32`	Microsecond of first frame in file

The data follows, in signed 32 bit integers. One must multiply by 9.85 and then divide by 256.0 to scale the data properly to acoustic pressure.

Note 1: Data dropouts occurred with the data recorder. The timestamps given for the first frame in the file are most likely incorrect. See the A/X 2 master timesheet for the "best guess" of timing.

Note 2: The channel number is different than the hydrophone number. The hydrophone number counts from the bottom of the array (hydrophone 1) to the top (hydrophone 30). The translation between channel number and hydrophone number is given below.

Tape 34 File 15:

This is not a stationary event. Rather, there is a high bearing rate change during this time. From the A/X 2 master timesheet:

Date	Time	Range (m)	Bearing (radians)	Bearing (degrees)	Speed, relative
YYMMDD	(UTC)	from array center	(east is 0)	(north is 0)	to array (m/sec)
980411	22:47:05	1205.0383	-1.572409	180.0924	0.3853
980411	22:47:20	1210.4598	-1.609104	182.1949	0.3614
980411	22:47:35	1218.5559	-1.644620	184.2298	0.5397
980411	22:47:50	1227.3850	-1.682698	186.4115	0.5886
980411	22:48:06	1238.0834	-1.720919	188.6014	0.6687
980411	22:48:20	1249.9575	-1.755517	190.5837	0.8481

Each file is 6002788 bytes. Shift-click in your browser, or get all the files via anonymous FTP at ftp://acoustics.mit.edu/ffp/34/

Array 1 2 3 4 5

Channel 1 / Hydrophone 15 1 1 1 1 1

Channel 2 / Hydrophone 14 2 2 2 2 2

Channel 3 / Hydrophone 13 3 3 3 3 3

Channel 4 / Hydrophone 12 4 4 4 4 4

Channel 5 / Hydrophone 11 5 5 5 5 5

Channel 6 / Hydrophone 10 6 6 6 6 6

Channel 7 / Hydrophone 9 7 7 7 7 7

Channel 8 / Hydrophone 8 8 8 8 8 8

Channel 9 / Hydrophone 7 9 9 9 9 9

Channel 10 / Hydrophone 6 10 10 10 10 10

Channel 11 / Hydrophone 5 11 11 11 11 11

Channel 12 / Hydrophone 4 12 12 12 12 12

Channel 13 / Hydrophone 3 13 13 13 13 13

Channel 14 / Hydrophone 2 14 14 14 14 14

Channel 15 / Hydrophone 1 15 15 15 15 15

Channel 16 / Hydrophone 30 16 16 16 16 16

Channel 17 / Hydrophone 29 17 17 17 17 17

Channel 18 / Hydrophone 28 18 18 18 18 18

Channel 19 / Hydrophone 27 19 19 19 19 19

Channel 20 / Hydrophone 26 20 20 20 20 20

Channel 21 / Hydrophone 25 21 21 21 21 21

Channel 22 / Hydrophone 24 22 22 22 22 22

Channel 23 / Hydrophone 23 23 23 23 23 23

Channel 24 / Hydrophone 22 24 24 24 24 24

Channel 25 / Hydrophone 21 25 25 25 25 25

Channel 26 / Hydrophone 20 26 26 26 26 26

Channel 27 / Hydrophone 19 27 27 27 27 27

Channel 28 / Hydrophone 18 28 28 28 28 28

Channel 29 / Hydrophone 17 29 29 29 29 29

Channel 30 / Hydrophone 16 30 30 30 30 30

Tape 35 File 17:

Range: 7101 meters. Bearing: -2.837426 radians. Depth: 60.65 meters.
Each file is 6002788 bytes. Shift-click in your browser, or get all the files via anonymous FTP at ftp://acoustics.mit.edu/ffp/35/

Tape 36 File 7:

Range: 15342 meters. Bearing: 3.112526 radians. Depth: 60.65 meters.
Each file is 6002788 bytes. Shift-click in your browser, or get all the files via anonymous FTP at ftp://acoustics.mit.edu/ffp/36/

FFP Comb Sequence

Calibration of the J-15 source was performed by Howard Lynch of TRANSDEC at SPAWAR Systems Center, San Diego. The transmitted power spectral density of the comb sequence can be found here.

Last updated: 991004
Comments/Questions: pmd@alum.mit.edu

Array	1	2	3	4	5
Channel 1 / Hydrophone 15	1	1	1	1	1
Channel 2 / Hydrophone 14	2	2	2	2	2
Channel 3 / Hydrophone 13	3	3	3	3	3
Channel 4 / Hydrophone 12	4	4	4	4	4
Channel 5 / Hydrophone 11	5	5	5	5	5
Channel 6 / Hydrophone 10	6	6	6	6	6
Channel 7 / Hydrophone 9	7	7	7	7	7
Channel 8 / Hydrophone 8	8	8	8	8	8
Channel 9 / Hydrophone 7	9	9	9	9	9
Channel 10 / Hydrophone 6	10	10	10	10	10
Channel 11 / Hydrophone 5	11	11	11	11	11
Channel 12 / Hydrophone 4	12	12	12	12	12
Channel 13 / Hydrophone 3	13	13	13	13	13
Channel 14 / Hydrophone 2	14	14	14	14	14
Channel 15 / Hydrophone 1	15	15	15	15	15
Channel 16 / Hydrophone 30	16	16	16	16	16
Channel 17 / Hydrophone 29	17	17	17	17	17
Channel 18 / Hydrophone 28	18	18	18	18	18
Channel 19 / Hydrophone 27	19	19	19	19	19
Channel 20 / Hydrophone 26	20	20	20	20	20
Channel 21 / Hydrophone 25	21	21	21	21	21
Channel 22 / Hydrophone 24	22	22	22	22	22
Channel 23 / Hydrophone 23	23	23	23	23	23
Channel 24 / Hydrophone 22	24	24	24	24	24
Channel 25 / Hydrophone 21	25	25	25	25	25
Channel 26 / Hydrophone 20	26	26	26	26	26
Channel 27 / Hydrophone 19	27	27	27	27	27
Channel 28 / Hydrophone 18	28	28	28	28	28
Channel 29 / Hydrophone 17	29	29	29	29	29
Channel 30 / Hydrophone 16	30	30	30	30	30