Computer
- You require a PC running Win95 / 98 / Me / NT / 2000 / XP / Linux,
SUN - Solaris, or a Macintosh running OS 8, 9 or X.
- Microsoft Explorer 4x (or higher) or Netscape 4x (or higher).
- The latest version of the Java plug-in from SUN (most newer
PC's come with this version of Java plug-in already installed).
- A good-quality sound card.
- All applications on your computer, except your web browser, must be closed.
- All sound-processing features on your sound card such as "Bass Boost",
tone control, reverbaration, DSP, etc. must be disabled.
- The volume on your computer and/or audio system must be at the level you usually use or lower.
You can lower volume by going to volume adjustment in the Mixer software. In Windows this is done
by selecting Start -> Programs -> Accessories -> Entertainment -> Volume
Control. Check your computer manual for other platforms.
Java Plug-in & System Test
- When you click on the "Proceed" button located further down the page
the Hearing Test will be launched.
- If you require a Java plug-in, follow the instructions to download it.
If no automatic install takes place make sure to double-click on the downloaded
.exe file to install it. You can manually download Java plugin, JRE 1.4.2
for a particular computer platform from
SUN's website (this will take about
3-10 min).
- Make sure that Java version 1.4.2 or higher is used during testing
(multiple Java environments can co-exist on your computer).
Headphones
- Should be of good quality (for example AKG K-270 or KOSS R/80).
- Closed-type headphones are the best choice as they
reduce outside noise.
- Headphones must be plugged into the headphones output on your
computer. The headphones output is usually marked as such and it is most often located on
the back pannel of the computer. In most cases, it is a miniature stereo
output, similar to the output socket on a portable CD player. If necessary, refer to your
computer manual for more details.
Earphones
- Should be of good quality (for example some models of SONY, Panasonic, JVC, AKG, KOSS).
- Miniature earphones (or earbuds) can be turned into good-quality "closed-type headphones"
by wearing earmuffs over them. Good earmuffs (for example Thunder 29 from Howard Leight) offer
about 29-31 dB noise
reduction (better than most headphones). You can buy them in many hardware
stores for about $20 US. Earmuffs can also be used
to protect your hearing in noisy situations.
- Earphones must be plugged into the headphones output on your
computer (as described above).
Speakers
- Should be of good quality (for example ALESIS 'Monitor One Mk2' or 'M1 Active Mk2').
- Good quality speakers will have flat frequency response in 40 Hz - 20,000 Hz range
and low harmonic and intermodulation distortions.
- Speakers must be connected to the power amplifier. Amplifier should get its signal
from line (or headphones) output on your computer. They are usually marked as such and
most often located on the back pannel of the computer. In most cases, it is a miniature
stereo output, similar to the output socket on a portable CD player. In some cases there
are RCA-type connectors on the soundcard. If necessary, refer to your computer manual
for more details.
Noise
- For auditory and psychoacoustic experiments, all noisy equipment (such as fans, radios,
etc.) must be switched OFF to minimize background noise that can interfere with the tests.
- You should perform the tests when the noise level in the room and outside is at its lowest.
Safe Sound Levels / Calibration of WWW DFG
- DFG modules can be used in combination with WWW SLM in a variety of very interesting
acoustical, audio, auditory, psycho-acoustic, and electronic experiments. However, caution
is required in the adjustment of safe sound levels to protect your hearing and audio equipment.
- SPL (Sound Pressure Level) should be limited to a maximum of 80 dB SPL for several minutes
of exposure and to a maximum of 60 dB SPL for several hours of exposure.
- Sound calibration should be performed with a properly working reference SLM (Sound Level
Meter). Volume calibration can be performed by using volume control in the computer
Mixer software or externally on the powered speakers or amplifier.
- For calibration of headphones or earphones one needs SLM (for example from Radio
Shack, B&K, etc.) and an acoustical coupler (such as DR1, DR2, or DR1-R from Digital Recordings).
- Warble Tone Generator (one of the DFG modules) should be used for most accurate
calibration. Calibration should be performed using 1000 Hz and 0 dB settings in the DFG
module. Maximum SPL should be set to 60 dB, 70 dB or 80 dB (maximum for short durations) with
the aid of a reference SLM (Sound Level Meter) and a proper acoustical coupler (for headphones
and earphones).
Microphone Calibration for WWW SLM
- Digital Sound Level Meter can be used with one or two microphones. In this case you
are able to measure simultaneously sounds at different points in the room or compare
sounds in two separate rooms - for example for TL measurements. If you are using two
microphones, make sure that they are identical or similar if you want to compare
results between them. Connect microphone(s) to line input(s) of your soundcard via mic
preamplifier, audio mixer or even old tape recorder with mic inputs.
- Calibration of SLM (Sound Level Meter) is only needed if you want to make measurements
of absolute SPL (Sound Pressure Level) in dB. If you are compering sound levels, for
example from two different speakers, or measuring frequency response of a component
(acoustical or electrical signal), only relative results may be of interest.
- In order to measure absolute value of SPL, calibration is required. There are
several methods to do this, two of which are:
First method involves generation of 1000 Hz warble tone in
speakers at SPL level of 60 dB. Measure this level with a good Sound Level Meter (for example
from Radio Shack, B&K, etc.). Adjust level on a DFG module until the reference SLM reads 60 dB on
the fast C or linear scale. Set WWW SLM to 20 dB - 120 dB range (for example). Place the mic which
you are using with WWW SLM very close to the reference SLM. Now adjust the level on the mic preamp or
the audio mixer until WWW SLM reads 60 dB on SPL [dB] RMS scale (large green display).
Second method involves generation of 1000 Hz warble
tone in headphones at SPL level of 60 dB. Measure this level with a good Sound Level Meter
(for example from Radio Shack, B&K, etc.) and an acoustical coupler (such as DR1, DR2, or DR1-R
from Digital Recordings). Adjust the level on the DFG module until SLM reads 60 dB on the fast C or
linear scale. Set WWW SLM to 20 dB - 120 dB range (for example). Replace the reference SLM
with the mic you are going to use (both mics should have the same diameter to fit into
an acoustical coupler). Now adjust the level on the mic preamp or audio mixer until WWW SLM reads
60 dB on SPL [dB] RMS scale (large green display).
- If calibration was performed correctly
you can use WWW SLM in 0 - 22,000 Hz and 20 - 120 dB range. Do not change SPL RANGE
after calibration, as calibration is only valid for this SPL range! Precision of WWW SLM
will depend on the quality of your soundcard and used microphone(s). With good equipment you
can expect +/-0.01 dB repeatability of measurement. Good microphones are produced by AKG, B&K,
Audio Technica, Sennheiser, etc.
Hearing Protection
- For audio and acoustical experiments involving sounds produced by speakers at levels
higher than 60 dB hearing protectors such as earmuffs (for example 'Thunder 29' from Howard
Leight) or earplugs (for example 'Classic' from EAR) should be used.
- Hearing protectors have only limited attenuation capabilities (usualy 10 to 30 dB
depending on the used frequency and the type of the protector). Therefore, caution should be
used. SPL levels in the ear after attenuation should not be higher than 80 dB for short
duration and 60 dB for longer duration.
- If at any time during the experiment you feel any discomfort, you should stop
the experiment immediately and switch OFF the sound source.
Safety
- Volume calibration is the first step in any acoustical, audio and auditory testing and
experiments. You must follow the provided instructions to set safe sound levels in order to
protect your hearing and your computer/audio equipment.
- if at any time during the testing or experiments you feel any discomfort or
you find volume levels too high switch OFF the sound source and stop the test immediately.
- Volume Calibration should be performed with the aid of SLM (Sound Level Meter) and
proper acoustical coupler (for headphones and earphones). Please see our website for more
information about acoustical couplers (DR1, DR2 and DR1-R).
Copyrights / License
- All sounds produced by DFG modules are licensed by Digital Recordings for your personal,
environmentally-responsible and non-commercial use only.
- Reproduction, duplication or public use or broadcasting of DFG sounds is strictly prohibited.
- Recording, editing, reuse, reformatting, resynthesizing, remixing, filtering or any other
type of processing for use in another product or for resale is strictly prohibited without written
license and permission from Digital Recordings.
- Commercial use and resale of WWW Instruments and DFG products as well as sounds produced by DFG
package is strictly prohibited without written license and permission from Digital Recordings.
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