Guide to Kresge EchoMaster Page 1
Guide to the Use of Kresge EchoMaster: A Program for Quantification
and Analysis of TEOAEs
Kresge EchoMaster Software developed by Han Wen, M.S.B.E.
Current Version: 4.0 (1998)
Guide written by Linda J. Hood, Ph.D.
Professor, Kresge Hearing Research Laboratory
Department of Otolaryngology and Biocommunication
LSU Health Sciences Center, New Orleans
The EchoMaster Program was developed at Kresge Hearing Research
Laboratory by Han Wen, M.S.B.E., to compare changes in TEOAEs obtained under
different conditions in efferent suppression experiments. The current version 4.0 of the
EchoMaster software is compatible with the Otodynamics ILO systems file structure
through Version 5.0 of the ILO software.
The EchoMaster software has been made available to researchers upon request
since 1993. This software is provided at no charge to the research community with the
agreement that proper credit will be given in any publications and that it will not be
copied for commercial purposes.
EchoMaster is organized into five modules: Input, Output, Dynamic Time Zone
Analysis, Multiple Time Zone Analysis, and Frequency Analysis.
Time zones of 1, 2, or 3 msec within the 20 msec time window of TEOAEs
recorded using an ILO system are selectable to compare individual TEOAEs to the
noise levels, compare two TEOAEs, or compare means of sets of up to 60 TEOAEs.
Comparisons are made of amplitude (RMS), cross correlation (Rxy), time delay (Del),
and echo spectra (FFT method). Data can be saved into ASCII files for statistical
In the time domain, the program calculates root-mean-square (RMS) differences
(dB) and cross-correlation values (or signal-to-noise ratios if comparing an echo with its
background noise). Time regions are targeted in one of two modes: overlapping or non-
overlapping. In the overlapping mode, step sizes range from 0.12 to .8 msec, and, in
the non-overlapping mode, step sizes range from 1 to 3 msec. Curves are displayed to
give an overview of the differences between selected echoes.
Guide to Kresge EchoMaster Page 2
In the frequency domain, Welch’s fast Fourier transform (FFT) method is
employed to estimate echo spectra. Welch’s method reduces the spectral normalized
random error as compared to conventional methods of estimating spectra directly by
FFT. Eight commonly used windowing functions are available including Rectangular,
Triangular, Hanning, Hamming, Blackman, Blackman-Harris, Gaussian, and Kaiser. In
the results, the echo power spectra, cross power spectra, cross spectral phase angle,
and magnitude squared coherence are evaluated.
Use of the program
EchoMaster is a DOS-based program that does not utilize a mouse or windows
icons. It can be opened through a DOS or windows environment. To run the
EchoMaster program, type "EM40". When the title screen appears, press the enter
(return) key to move to the next screen.
The main menus are shown at the start of the program. These menus and a
brief statement of their functions are as follows:
Menu 1 Options Set up program parameters
Menu 2 Echodata Retrieve OAE data from ILO files
Menu 3 Analysis Analyze OAE data
Menu 4 Statistics Display and print statistical summaries
Menu 5 Print Print data, curves, and graphs
Menu 6 Save Save EchoMaster results to disk
Menu 7 Quit Exit EchoMaster
Menu 1: Options
When the program begins, the “Echo Duration” submenu is displayed which
allows selection of resolutions ranging from 26 µsec per point to 300 µsec per point.
For ILO files, the default setting (highlighted) of 40 µsec per point is selected. Other
options shown on Menu 1 relate to the echoes that are shown, the step size, windowing
functions for spectral analyses, and printer set-up and use options.
Menu 2: Echodata
The first two options allow location of the disk and path containing the OAE data
to be analyzed. The remaining options provide for retrieval or single or multiple OAEs.
To retrieve a single OAE, highlight either “Current Echo A” or Current Echo B”
and press the enter key. At this point, a list of the available files is shown. Move the
cursor to the desired file and press enter. The OAE test parameters and data from the
ILO file are shown. Pressing the space bar retrieves the file into EchoMaster memory.
Guide to Kresge EchoMaster Page 3
To retrieve more than one OAE file into a buffer and obtain the mean of the OAE
files, highlight either “Echo(es) in Buffer A” or “Echo(es) in Buffer B” and press return.
Use the up or down arrows to locate the first file to go into the buffer and press return.
A check mark will appear next to the file name. Continue this process for up to 60
OAEs. When all OAEs are selected, move the cursor to “Return” which is at the top of
the OAE data list using either the up arrow key or page up key. Pressing the return key
will return to the buffer sub-menu.
Highlight “Get Mean and Exit” to obtain the mean of the selected files. Enter a
name for the mean data. (Note that when a new set of data are entered into a buffer,
the user must first empty the buffer using the “Flush Buffer” option.)
Menu 3: Analysis
Comparisons that can be made in the EchoMaster analysis include Echo A with
its related noise, Echo B with its related noise, and Echo A with Echo B.
To compare an OAE with its noise, select either “Echo A and N” or “Echo B and
N” and press enter. At the bottom of the screen, several function key and other
operations are shown. The user can move and locate the cursors across the OAE time
window display using the F1 and F2 keys, plot a signal-to-noise ratio (SNR) curve using
the F3 key, and display the OAE spectrum using the F4 key.
To compare two OAEs, select "Echo A & B" and press enter. The comparison
that will be made is of two echoes (or two buffers containing series of echoes). The
options at the bottom of the screen are the same as for echo and noise comparisons,
with the exception of the F3 option. This changes from “SNR” to “R R D” which
provides comparisons of amplitude difference (RMS), cross correlation (Rxy), and time
delay (Del). To select the curves (one, two, or three) to be viewed in the upper half of
the screen, use submenu option F1 (“Show R R D”) under the F3 (“Show R R D”) menu.
The amplitude display scale (Y axis) can be changed using the “*” key to
increase the display amplitude of the OAE and the “/” key to decrease the display
amplitude of the OAE. When either the signal-to-noise ratio or RMS amplitude
difference (F3) is selected, a curve or curves are displayed on the top half of the screen.
Points on these curves are displayed at 1, 2, or 3 msec intervals, depending on the
selection made in the options menu (Menu 1).
Menu 4: Statistics
Statistical data related to the time period and spectra can be displayed and
printed in this menu. “Zoned Echoes” provide statistical information about the time
period (zone) defined by the positions of the cursors. “Echo Spectra” provides power
spectrum statistical data.
Guide to Kresge EchoMaster Page 4
Menu 5: Print
The print menu contains options to print hard copies of various data, curves, and
graphs. Desired items can be selected for printing in a user determined order. The
default setup sends a page forward command to the printer after each item is selected.
This option can be turned off in the options menu (Menu 1) to allow printing of several
items on a single page.
Menu 6: Save
EchoMaster analysis results can be saved to disk by using options available in
the “Save” menu. The overall echo amplitude data, zoned echo amplitude data, values
of the amplitude (RMS), cross-correlation (Rxy), and time delay (Del) plots, and the
spectral analysis values can be saved. Each item saved can be appended into an
existing file or saved as an individual file.
Menu 7: Quit
Highlighting “Yes” exits the EchoMaster program.
For Further Information:
Berlin, C. I., Hood, L. J., Hurley, A. E., Wen, H., & Kemp, D. T. (1995). Binaural noise
suppresses linear click-evoked otoacoustic emissions mare than ipsilateral or
contralateral noise. Hearing Research, 87, 96-103.
Berlin, C. I., Hood, L. J., Wen, H., Szabo, P., Cecola, R. P., Rigby, P., & Jackson, D. F.
(1993). Contralateral suppression of non-linear click-evoked otoacoustic emissions.
Hearing Research, 71, 1-11.
Hood, L. J., Berlin, C. I., Hurley, A., Cecola, R. P., & Bell, B. (1996). Contralateral
suppression of transient-evoked otoacoustic emissions in humans: Intensity effects.
Hearing Research, 101, 113-118.
Hood, L. J., Berlin, C. I., Hurley, A., & Wen, H. (1996). Suppression of otoacoustic
emissions in normal hearing individuals. In C. I. Berlin (Ed.) Hair Cells and Hearing
Aids (pp. 57-72). San Diego CA: Singular Publishing Group, Inc.
Wen, H., Berlin, C. I., Hood, L. J., Jackson, D. F., & Hurley, A. (1993). A program for
quantification and analysis of transient evoked otoacoustic emissions. ARO Abstracts,
Guide to Kresge EchoMaster Page 5
Appreciation is expressed to David Kemp, Ph.D. for his help in characterizing the ILO
file structure. The developer of the program (H.W.) thanks Stephen Neely, Ph.D. and
Intelligent Hearing Systems Corporation. The development of Kresge EchoMaster was
supported by NIH NIDCD P01-DC000379, Kam’s Fund for Hearing Research, and the
Louisiana Lions Eye Foundation.