bcAnalyze 1.0
Manual
ecoObs GmbH, Reindelstrasse 2, 90402 Nürnberg, www.ecoobs.de
ecoObs GmbH - bcAnalyze 1.0 - 
Legal
The application bcAnalyze was created according to best knowledge and thoroughly tested. Nevertheless its failure free use can not be guaranteed under no
circumstance. If you encounter errors, we ask you to report these to us so we can
try to improve the application for you.
We - the ecoObs GmbH - grant you a license to use the applications, a license that
does not entitle you to sell the application to others. Within the first 30 days starting
from the first start of the application it can be used free of charge (trial period). After
30 days the applications can only be started with a valid license obtained from us.
In no event can we be held liable for any direct, indirect, incidental or any consequential damages risen by the use of the software.
Prerequisites
bcAnalyze was developed for Apple Computers running OS 10.5 or newer. It runs
on PPC as well as Intel Macs and expects at least 1024 MB of memory. Hard disk
size should be big enough to hold the recordings from the batcorder.
Redaction
Responsible for the contet of this manual are:
Ulrich Marckmann, NycNoc GmbH
Dr. Volker Runkel, ecoObs GmbH
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- ecoObs GmbH - bcAnalyze 1.0
Content
Introduction to bcAnalyze
4
bcAnalyze‘s User Interface
5
Basics
6
Basic Functions
8
Installation
Quick start 4
4
Definitions
6
Open Files
Mark and zoom
Preferences for Desktop, Tool Bar, and Display
8
9
9
Analysing Signals
11
Miscellaneous
17
Wave Form Statistics
Spectrum
Sonogram
Automated Identification and Measurement of Calls/Signals
Licensing
Updates
Error Reports
Short Cuts
11
11
12
14
17
17
17
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ecoObs GmbH - bcAnalyze 1.0 - Introduction to bcAnalyze
Introduction to bcAnalyze
Congratulations to your decision for bcAnalyze. You have purchased a sound
analysing program, which has specifically been designed for the analysis of bat
echolocation calls. It is harmonised with all hard- and software components of the
batcorder System. Of course you can also analyse recordings of other systems.
The main focus of this program lies in a fast display and analysis of sound recordings, with an easy and intuitively operated user interface. Ultrasonic sound signals
are quickly identified, measured and results are displayed by a special algorithm,
which is also used by our other program bcAdmin. Therefore, bcAnalyze is a highly
efficient tool to analyse signals, to extract measured values, and to compare them
with the original recording files. bcAnalyze is aimed at both, beginners in sound
signal analysis and experts who need a fast and precise tool.
Installation
System requirement for bcAnalyze is a regular Apple Computer (PPC / Intel) with
operating system OS X 10.5 or higher. We also recommend a central memory of
at least 1 GB.
You can find an installation package for a complete installation with all components
on our homepage. All you need is administrator access to your computer.
Quick start
bcAnalyze is designed like other common programs for sound analysis so that
experienced users quickly can manage our program. It starts by double clicking on
any .raw file in the Finder. You can also find and start bcAnalyze in the application
folder of your computer. After opening a sound file, this recording will be displayed
as a oscillogram (wave form). Results from bcAdmin are additionally shown if bcAdmin has already measured calls and saved values to a .bcCalls (or .data) file.
You can select ranges with your mouse and generate a spectrum or a sonogram.
Identified calls can quickly be selected with the tab key and sonograms of selected
calls are generated with ⌘+R. More details are to be found in the next chapters.
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bcAnalyze‘s User Interface - ecoObs GmbH - bcAnalyze 1.0
bcAnalyze‘s User Interface
A. Menubar
B. Toolbar
C. Main window
E. Oszillogram
D. Inspector
F. Call Preview
A: Menubar: all functions of bcAnalyze.
B: Toolbar: a quick access to several commands.
C: Main window: shows the content of a sound file.
D: Inspector: quick access to clearly arranged information of the file, the selected
call, identified signals, and sonogram preferences.
E: Oscillogram: Display of wave form of the file.
F: Call Preview: Measured points of the call analysis in time-frequency pattern.
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ecoObs GmbH - bcAnalyze 1.0 - Basics
Basics
Definitions
pressure
Sound
Sound is an oscillation of air pressure which spreads as a wave with a velocity of
ca. 340 m/s. An oscillation of one specific frequency is called a pure tone, which
results in a sinus wave when outlined over time. Such an illustration is called wave
display or oscillogram.
time
Frequency
The frequency of sound is defined by the number of oscillations per second [Hz Hertz]. Depending on the frequency sound can be classified as infrasonic sound
(below 16 Hz), audible sound (16 Hz up to 20 kHz, audible for humans), and ultrasonic sound (20 kHz up to 1 GHz). In contrast to a pure tone, sound (in terms of
noise) is composed of many frequencies that change over time. A tone is a periodic
signal generated by several pure tones.
Microphone
A pressure sensor (microphone) detects changes in air pressure and transforms
these into electrical pulses. These pulses ideally (exact linear transformation) form
a wave as explained above. This is still an analogue signal (continuous signal),
which has to be transcribed in discrete time and amplitude steps in order to digitalise it.
Sample Rate
The sample rate defines the time interval for reading out the signal. The sample
rate has to be significantly higher than the frequency of the respective signal. For
an accurate digital reproduction of an acoustic signal, the sample rate has to be
twice as high as the maximal frequency of the analogous signal (Nyquist-Shannon
Sample Rate Theorem). A audio CD for example is recorded with a sample rate
of 44.1 kHz in order to reproduce human audible frequencies from 50 Hz up to 20
kHz. For bat calls the sample rate should be at least 250 kHz because echolocation calls can reach up to 125 kHz. We recommend a sample rate of 500 kHz for
the automated analysis with bcAnalyze.
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Basics - ecoObs GmbH - bcAnalyze 1.0
Amplitude Resolution
This attribute denotes the possible amount of amplitude values for digitalisation.
For a resolution of N exactly 2N values have to be available, e.g. resulting in 65536
steps for 16 Bit. Generally, in acoustic digitalisation each sample becomes digitalised with at least 16 Bit resolution, which corresponds to a theoretical dynamic of
96 dB. We recommend to apply at least 16 Bit for a feasible analysis of ultrasonic
signals.
Sound Pressure Level, Override (Clipping)
The sound pressure level (loudness) can be specified linearly (pressure in Pascal
or voltage in Volt). However, it is more common in acoustics to use a logarithmic
scale: Decibel dB, which describes the loudness with the common logarithm of the
ratio of two levels. Therefore it is a relative unit without dimension, representing an
increase with positive and an attenuation with negative values. dB specifications
are often related to a standardised reference value: dB SPL is referenced to the
human auditory threshold at 1 kHz and indicates how much louder a signal is as
compared to this value. The great range between quiet and loud can be comfortably expressed by this unit. For instance, a difference of 80 dB between two signals
relates to a voltage ratio of 1:10.000. As a convenient rule of thumb: a doubling of
the sound pressure level (respectively voltage) results in 6 dB, a tenfold increase
in 20 dB difference.
An override results if the analogue signal is louder than the input of the digitalisation device (AD-Converter). The sinus wave is clipped and the signal gets adulterated. This also applies to analogue amplifiers as they cannot produce a linear
amplification (distortion). In frequency analysis this causes deceptive frequencies.
Frequency Analysis
There are several methods for an analysis of sound signals. A simple and feasible method is the zero crossing analysis:
it calculates the oscillations per second
(frequency) by counting how often the
zero point is crossed and establishes a
periodogram. With many consecutive
measures a frequency progression over
time can be constructed (see Figure to
your right-hand side). The Fourier Transformation is the most common method
to analyse an acoustic signal which is composed of several frequencies. This elaborate technique separates a periodic signal to its single frequency components.
bcAnalyze applies a slightly less complex method, the Fast Fourier Transformation
(FFT) for the calculation of spectra and sonograms.
Compared to a spectrum, which illustrates the frequency classes of a signal, a
sonogram also depicts the temporal pattern of these frequencies.
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ecoObs GmbH - bcAnalyze 1.0 - Basic Functions
Basic Functions
Open Files
You can open files with the Open- and Open Recent-Command from the File Menu.
Supported are common WAVE-files (extension .wav) and „batcorder“ files (RAW).
WAVE-files contain file information, such as sample rate and amplitude resolution
that are automatically read by bcAnalyze. Some WAVE files which were compiled
by programs that are not conform with official wav-specifications may cause errors
when opened by bcAnalyze (compressed WAVE-files are incompatible). RAW-files
(extension .raw) are structured like WAVE-files but lack the code of file information
in their header. They are interpreted with 500 kHz and 16 Bit by default. The user
is prompted to choose a track for display if an audio file contains more than one
audio track (e.g. stereo files). bcAnalyze also asks whether a WAVE-file with a low
sample rate (< 100kHz) is to be opened as a time expanded recording.
Opened files are displayed in the document window as wave forms. The height
of the oscillation is pictured linearly to the loudness (in voltage). Signals are overdriven if their amplitudes reach the upper border.
Magnify tool
Zoom control
Lock selection
Normalise
At the lower left side of the window you can find a button for the normalisation of
the oscillogram: the window scale is adjusted in order to display the whole signal.
Scale and captions of the time axis are milliseconds (1000 ms are one second).
Already existing measures are automatically shown in the call preview above the
sound track.
You can close the file by clicking on the red button in the upper left corner or by
choosing the command Close File in the file menu. With Save as from the file menu
you can choose to save in WAVE or RAW file format.
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Basic Functions - ecoObs GmbH - bcAnalyze 1.0
Mark and zoom
After a file is opened the sound signal is completely displayed as an oscillogram.
There are two options available for magnifying selections. You can magnify a selection of the track with the zoom tool (magnifier - lower left side of the document
window): just press and hold the mouse button and select a region by drawing
a frame around it. With releasing the mouse button this section is automatically
magnified. Please be aware that normal selection is not possible as long as the
magnify tool is active.
You can find an alternative zoom bar on the lower right side of the document window: the magnification is continuously adjustable by shifting this ruler. A maximal
magnification or downsizing is achieved by clicking on the corresponding buttons
beside the zoom bar. From a specific magnification on each sample of the wave is
displayed (true-sample display) and before an approximation is applied in order to
accelerate the image formation. This approximation is based on maximum RMS
values of small overlapping windows that are calculated throughout the acoustic
signal. Negative pressure values arise by mirroring positive maxima. Thereby, characteristics like acoustic noise and offset can be inspected in true-sample display
only.
By hovering the cursor over the oscillogram, values of amplitude in voltage and
associated time values in milliseconds of the current cursor position are displayed
below the wave form.
You can draw a red frame around an area in the oscillogram with your mouse. This
part of the sound file is then selected for further editing (sonogram, spectrum, etc.).
The selection module of the Inspector reports duration, starting and ending point of
the marked area, which can also be altered with this tool. Sample rates, duration
and zoom level are shown in the sound file specs module. In the edit menu you
can select the whole track and clear selections. There is also a button to clear selections in the upper left corner of the tool bar. You can also lock a selection with
the lock symbol on the left side below the oscillogram in order to protect it against
unintended changes.
It may be difficult to find again a marked section with high magnifications. In order
to view a marked selection bcAnalyze provides the function Scroll to Selection in
View from the menu bar and the button Show Selection in the tool bar. If you then
zoom in or out, the window position is fixed optionally at the left window frame or in
the centre of the oscillogram (see: Preferences). In the preferences you can also
set up whether the current selection serves as a reference for zooming.
Preferences for Desktop, Tool Bar, and Display
By moving the border between the oszillogram and call preview you can change
the vertical division. The toolbar can be customised with the function Customise
Toolbar in the View sub-menu of the menu bar: functions can be added or excluded
by drawing buttons to or from the toolbar; you can also hide the toolbar.
In the Preferences panel you can also change colours of wave lines, measure
points, background, and selections for the oscillogram and call preview. Colour Re9
ecoObs GmbH - bcAnalyze 1.0 - Basic Functions
set restores the default colours.
Preferences are stored for each
user‘s account.
You can set up in the sub-menu General whether batIdent‘s/
bcDiscriminator‘s species determinations should be displayed
beside call markings. Here you
can also adjust the grid scale and
frequency range of the call preview window. For customisation
options of the sonogram please
refer to chapter on sonagrams.
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Analysing Signals - ecoObs GmbH - bcAnalyze 1.0
Analysing Signals
Wave Form Statistics
Basic wave form statistics can be found in the the information sub-menu of the inspection window. The drop-down
menu shows the DC Offset (offset from the base line) and
maximum amplitudes of positive (Max.) and negative halfwaves (Min.) for a marked section (linear percentage and
dB). These values are normalised to a a sinus tone of maximum amplitude (maximum gain). The effective value of
loudness is shown as mean RMS (mean signal volume).
The field RMS Window allows you to change the window
size from which values of RMS and DC Offset are calculated. This window should not exceed the size of the signal.
If the window is smaller than the signal values are calculated several non-overlapping windows. Calculations can be
refreshed with the button Calculate RMS.
Spectrum
The frequency spectrum is determined by a Fourier Transformation and shows the amplitude distribution of frequencies of a signal. bcAnalyze employs the algorithm of a Fast Fourier Transformation (FFT). A spectrum does
not contain any time information and is generally calculated from a single window
(section of analysed sampling value). It is very accurate concerning the frequency
analysis.
The window function of the spectrum determines
the FFT-calculation‘s weighting of sampling values
within this section (window). There are several window functions available (e.g.: rectangle, hanning,
flat top). The basically differ in how much values at
the edges are considered. It is advisable to use a
rectangle for a spectrum because then all sampling points are weighted equally within this window.
The frequency resolution increases with the window size.
Calculations are possible for windows with the
size of 2N samples (N: integer). bcAnalyze applies
a procedure called zero padding in order to analyse sections of any size: zeros are added at the
start and at the ending of a selected section until a
length of 2N is accomplished.
Realisation:
For calculating a spectrum select a piece of the audio track. We recommend to
select pieces shorter than 222 samples because otherwise calculations become too
extensive (222= 4.194.304 samples equal 8 seconds of sound at 500 kHz sampling
rate). Click the button Spectrum from the toolbar or select Calculate Spectrum from
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ecoObs GmbH - bcAnalyze 1.0 - Analysing Signals
View in the menu bar. Then a window pops up with the calculated spectrum.
The graph shows amplitudes of frequencies on a logarithmic scale. The window
size (from which the spectrum has been calculated) and the resulting amplitude
resolution is shown on the left hand side below the spectrum. The applied window
function is displayed in a drop-down menu in the lower right corner. When you
move your mouse across the window the cursor becomes a harmonic cursor (red
and green lines) displaying frequencies and amplitudes for the current cursor position. You can open a context menu with a right click and save the spectrum as
a picture (with different formats) or as a text file. You can also select a smoothing
function that applies a moving average across an adjustable amount of frequency
classes. In this case the colour of Frequency Resolution changes to red.
Sonogram
A sonogram is a two-dimensional illustration of the frequency over time and is composed of many spectra over short time intervals. The amplitudes of frequencies is
encoded in colours. In contrast to the spectrum we recommend to apply other window function than the rectangle function since short windows would cause unwanted edge effects (side lobes; picket fences). The available window functions bear
different advantages and disadvantages. In general, window functions that render
frequencies accurately blur the temporal component and vice versa. Best windows
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Analysing Signals - ecoObs GmbH - bcAnalyze 1.0
for an accurate rendering of frequencies, e.g. for constant frequency signals (CF)
are the Hanning and the Hamming Window; for highly frequency modulated signals (FM) we recommend the Flat Top Window, and as a general standard window
the 7th Term Harris Window. Below you can see sonograms calculated with different window functions.
Different parameters influence the frequency and time resolution of a sonogram.
Adjustments can be made in the preference‘s sub-menu General and also in the
inspector‘s sub-menu Sonogram.
FFT Size determines the size (samples) of
the FFT-Analysis Window. With higher values the frequency resolution and the size of
the display increases. Overlap in percentage determines the window overlap for the
sonogram calculation. The higher this value
is chosen the more accurate will be the temporal resolution and the sonogram becomes
wider. Frequency and temporal resolutions
are displayed in the inspector next to the
corresponding parameters. In the lower
part of the preference‘s General menu (sonogram) you can change the display parameters of the Sonogram Overview (details,
frequency range, and contrast). After a sonogram has been created this overview
can be opened above the sonogram (Menu bar: View -> Sonogram Overview).
It displays the whole sonogram range in reduced size and thus helps navigating
within sonograms with high temporal resolution. With a frame that marks the current displayed section you can quickly move to an area of the sonogram just by
clicking on it. Details are automatically reduced if a too large part of the sound track
is selected for the sonogram calculation.
The sonogram‘s appearance can be modified by several
functions. You can change the colour style in the sonogram sub-menu Color of the inspector (levels of grey, fire,
coloured). With the button Inverted sonogram colours are
inverted. The colour coding of amplitudes can be further
customised with the sliders Gain, Range and Smooth and
a legend of the current colour encoding is shown in the
upper left corner of the sonogram.
When you move your cursor over the sonogram, time and
frequency of the current cursor position are presented in
the lower right corner of the window. You can also draw
a frame by holding down the left mouse button. Starting
time, length and frequency range of the selection are
given above the frame. By this you can quickly retrieve
length, starting and ending frequencies of bat calls from
the sonogram.
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ecoObs GmbH - bcAnalyze 1.0 - Analysing Signals
In the figure values with a distance of 0.1 ms of automated measurement are
shown as white points in the sonogram. This can be activated with Calls in the
menu bar. The next section describes how you can find calls automatically.
Automated Identification and Measurement of Calls/Signals
bcAnalyze comes with a new algorithm, which finds and measures ultrasound signals. We developed this function for our program bcAdmin, which extracts measurements from bat calls in an automated procedure.
In each call frequencies are measured every 0.1 ms over the whole signal. These
call measurements are shown by bcAnalyze in the call preview. With this procedure a recorded file can efficiently be scanned for signals without a manual and
time-consuming inspection of sonograms.
The Procedure and its Requirements
The procedure of automated call identification and measurement is based on a
complex zero crossing analysis with several consecutive working steps. First of all
the audio track is scanned for signals with a minimal loudness in order to exclude
signals that are too muted for a reasonable measurement. Subsequently a more
detailed analysis follows, which examines the signals, and decides whether they
are bat calls or just call-like sounds. Most background noises (e.g. locusts) and
echoes of signals are discovered and excluded from measurements. Finally bat
calls are measured: the signal‘s starting and end point is detected and the temporal frequency pattern is interpolated by 100 μs-steps (small gaps within the signal
are elided).
Some requirements have to be met for an error-free run of the procedure:
• the signal must contain ultrasonic frequencies (> 14 kHz),
• the signal must be tonal with a pronounced main frequency. In signals with harmonic oscillations either the fundamental or another harmonic has to be significantly louder than the other oscillations,
• the signal‘s length must be at least 1.5 milliseconds,
• the overlap of two signals with equal loudness cannot be measured (e.g. two
calls or a call and a loud echo),
• the signal‘s amplitude must be at least - 36 dB (this threshold is adjustable),
• the recordings‘ ambient noise level should not be too high. Recordings with the
Batcorder are most suitable.
• background noise should not excessively mask the signal,
• the recording should be monophonic.
Some parameters of the automated call identification and measurement are, like
in bcAdmin adjustable. In the advanced preferences threshold for loudness (dB
in relation to full conduction) and quality can be modified. Below these boxes the
amplitude threshold is shown as percentage of maximum amplitude (full conduction). Calls beneath the loudness threshold are not measured. The quality criterion
applies to the bat call identification: we recommend to adopt the default value of
20. With higher values also poor quality calls are identified and measured (e.g.
signals with a disadvantageous signal-to-noise ratio). A lower quality value leads
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Analysing Signals - ecoObs GmbH - bcAnalyze 1.0
to an exclusion of sub-optimal bat calls.
When you analyse batcorder recordings, bcAnalyze‘s loudness threshold should
conform to the threshold chosen at the batcorder. For both we recommend a value
of -24 dB because only saturated signals are measured and determined optimally.
The current threshold can be added as a line in the oscillogram with Show Analysis
Threshold in View from the menu bar.
The Automated Call Analysis‘ work flow
You can automatically search the audio track for call-like signals with Search Calls
in Calls from the menu bar (alternatively with the Search Calls button in the toolbar)
or you can load an existing bcAdmin signal file. These files are named as the associated audio track but hold the file extension „.bcCalls“ („.data“ in older versions).
If signal file and associated audio track are saved within the same folder identified
calls are automatically loaded to the call preview window. Example of a batcorder
audio track (raw) and its associated signal file:
250508-ZWEIM2XXXX-0004.raw
250508-ZWEIM2XXXX-0004.bcCalls
The function Search Calls saves identified calls only as a temporal signal file. You
can save it permanently by exporting the file with Export in Calls from the menu
bar. Choose the folder where the audio track is saved so that the call preview is
automatically loaded when you open this audio track in the future.
Calls are marked in the bar between the call preview window and the subjacent oscillogram. These tags are numbered consecutively and delineate the location and
length of the identified calls. The time scale of the call preview window matches the
oscillogram‘s scale so that call previews are shown directly above corresponding
tags. Calls, their starting points, length, starting and ending frequencies are now
listed in the inspector‘s sub-menu Call Values.
Find calls
navigate between calls
time/frequency at cursor
(Call Preview)
list of calls and measurements
Marker for
a found call
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ecoObs GmbH - bcAnalyze 1.0 - Analysing Signals
You can directly select a single call by clicking on a tag. This call is then framed in
the document window and highlighted in the inspector‘s list. This is a convenient
way to calculate a call‘s sonogram with accordant measured points displayed.
With the buttons Next and Previous in the tool bar and by Calls from the menu bar
you can comfortably navigate through the signals. You can also choose a call in
the inspector list; the oscillogram then shows the respective part of the audio track.
The call preview can be customised in the preference‘s sub-menu General. You
can adjust the grid scale and modify the lower and upper frequency limit. The appearance of the background, lines and measured points can be customised in the
Color sub-menu.
Displaying Species Assignments of batIdent / bcDiscriminator
If batIdent / bcDiscriminator already has analysed sequences these species assignments can be displayed call-wise beside call tags. In order to let bcDiscriminator
execute species assignments bcAdmin must provide a data file (with the extension
„.csv“) with measured values. You can order such a file in bcAnalyze with Create
bcDiscriminator File in Calls from the menu bar. bcDiscriminator‘s analysis then
starts and saves a file with determination results (extension „.res“) for bcAdmin and
writes results call-wise to the existing signal file (extension „.bcCalls“), from which
results automatically are taken when opening an audio track in bcAnalyze. With a
right click on a call tag a small panel opens with species abbreviation (see batIdent
/ bcDiscriminator manual) and assignment probability. You can turn on and switch
off this panel in the preference‘s General sub-menu.
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Miscellaneous - ecoObs GmbH - bcAnalyze 1.0
Miscellaneous
Licensing
bcAnalyze runs as a free trial version for 30 days. Afterwards a licence key can be
purchased from ecoObs GmbH. You will get a serial approved to your name and
an activation key. After you have filled in these information in the licence dialogue
the program is unlocked.
Updates
There are gratis updates available at regular intervals. You can check for updates
in the bcAnalyze sub-menu from the menu bar. In the preference‘s menu Updates
you can prompt the program to search for updates daily or once a week. If updates
are available they will be installed automatically.
Error Reports
In the case of a program crash an error report pops up when the program is restarted. You can add comments and send us this report, which helps us to improve
bcAnalyze. You can omit a report and delete it from the internal error list by selecting Omit. Otherwise the error report is shown as long as it is sent or deleted.
Short Cuts
Beside common shortcuts the following provide quick access to bcAnalyze‘s functions:
+/⇧+ 8
⇥
⇧+⇥
⌘+T
⌘+A
⌘+D
⌘+F
⇧+⌘+R
⌘+R
⌘+I
⌘+G
Zooming in the oscillogram
temporal magnification
go to next call
go to previous call
scroll to marking
select all
omit selection
find calls
calculate sonogram
show sonogram overview
open inspector
calculate spectrum
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