3. Psychoacoustics and HL
Recall that acoustics are physical properties of
a sound that are measureable (intensity,
frequency, wavelength)
Having a hearing loss does not change the
acoustics of sound or the sound wave itself
Hearing loss changes our psychoacoustic
perceptions of sound
4. Dynamic Range (DR)
DR=the range of intensities from the softest
sounds we can hear to the loudest sounds we
can hear
Imagefrom:hearingdirect.com
•In normal-hearing individuals, the
DR of our ears is 140 dB SPL
(from 0-140 dB)
•When we are referring to hearing
loss and the fitting of HAs, the
dynamic range refers to the range
of intensities from the threshold of
hearing (red circles) to the
loudness discomfort level (“L”)
•On the audiogram at right,
the DR at 500 Hz is 80 dB HL
and at 4000 Hz is 55 dB HL
5. The DR of
Human
Speech
The DR for the
voiced phonemes of
the English language
is about 30 dB wide,
which is depicted by
the speech banana,
at right.
Placing this speech
dynamic range within
the confines of the
patient’s residual
dynamic range is a
challenge in fitting
hearing aids.
Image from: firstyears.org
6. What happens when there is OHC
loss in the cochlea?
The response of the basilar membrane
becomes more linear
Loud sounds are not compressed as they once
were
As a result, loudness recruitment occurs
7. Loudness Recruitment
Recruitment is an abnormal loudness
perception in individuals with hearing loss
Oftentimes, patient’s with hearing loss report that
sounds that were once a comfortable volume are
now uncomfortably loud
Patient’s with SNHL have an elevated threshold
(sound has to be louder for them to hear it);
however, the loudness discomfort level does not
change significantly (it is the same as it was when
they had normal hearing)
As a result, the rate of loudness growth to their ears is
much more rapid
This results in loudness recruitment
8. WDRC
The purpose of wide-dynamic range compression
(WDRC) in modern hearing aids is to keep the
dynamic range (DR) of speech within the patient’s
DR in an attempt to recreate the non-linearity of a
normal cochlea
Remember, DR=the range of intensities from the
softest sounds we can hear to the loudest sounds
we can hear
The softest sound audible is determined by the
patient’s air-conduction threshold at each frequency
But, how do we know what the loudest sound level
that a patient can tolerate is?
By measuring the patient’s loudness discomfort levels
(LDLs)
9. To this point, we’ve discussed the standard
audiogram:
Puretone Audiometry
Air and bone conduction
Speech Audiometry
SRT and WRS
The following slides will discuss MCL, UCL,
and LDLs.
10. Most Comfortable Level (MCL)
The dB level of speech that the patient
feels is most comfortable.
Measured with a cold-running speech stimulus (i.e.
the Pledge of Allegiance, nursery rhyme, etc)
May be performed monaurally (one ear at a time) and
binaurally (both ears at same time)
Recall the advantages of binaural hearing?
The binaural MCL will be about 5 dB less than the individual
MCLs for fairly symmetric losses
Start at ~20 dB above the patient’s SRT and gradually
increase the intensity until the patient reports that the
speech is “comfortable”
Many clinicians perform word recognition testing at
the patient’s MCL
11. Uncomfortable Loudness (UCL)
The dB level of speech that the patient
feels is uncomfortable.
Measured with a cold-running speech stimulus (i.e.
the Pledge of Allegiance, nursery rhyme, etc)
Begin speaking at MCL and ascend until the patient
reports that speech is uncomfortable
Because MCL and UCL measure
loudness across a broad frequency
spectrum, they are difficult to use when
programming multi-channel hearing aids
12. Loudness Discomfort Level
(LDL)
The loudness discomfort level (LDL)
is the level at which the patient
reports sound to be uncomfortably
loud at specific frequencies
Stimuli: pulsed tones or narrow bands
of noise at .5, 1, 2, 3, and 4kHz
13. Why are LDLs important?
Research has shown that the range of what
patients rate as “uncomfortably loud” to be 20
dB
With that much potential variability between
patients, it is not wise to assume that a patient
has average LDLs (which is what
manufacturer software assumes AND all
manufacturers use different data for what is
considered average)
This may result in improper amplification and
rejection of hearing aids
14. Loudness Scaling to Determine
LDL
When performing
LDLs, the patient is
asked to rate the
loudness of
frequency-specific
stimuli (i.e. pulsed
tones)
It is best to provide
loudness anchors
such as the Cox
loudness descriptors
(at right) rather than
just having the
patient raise their
hand when the sound
is uncomfortable
Image from:
http://www.harlmemphis.org//index.php?cID=13
15. PATIENT INSTRUCTIONS FOR LDL
TESTING
Provide pt with loudness categories on previous slide
and state the following:
THE PURPOSE OF THIS TEST IS TO FIND YOUR
JUDGMENTS OF THE LOUDNESS OF DIFFERENT
SOUNDS.
YOU WILL HEAR SOUNDS THAT INCREASE AND
DECREASE IN VOLUME. YOU MUST MAKE A
JUDGMENT ABOUT HOW LOUD THE SOUNDS ARE.
PRETEND YOU ARE LISTENING TO THE RADIO AT
THAT VOLUME. HOW LOUD WOULD IT BE?
AFTER EACH SOUND, TELL ME WHICH OF THESE
CATEGORIES BEST DESCRIBES THE LOUDNESS.
KEEP IN MIND THAT AN UNCOMFORTABLY LOUD
SOUND IS LOUDER THAN YOU WOULD EVER
CHOOSE ON YOUR RADIO NO MATTER WHAT MOOD
YOU ARE IN.
16. Clinician Instructions for Measuring
LDLs
Begin slightly above threshold at 1kHz and use an
ascending technique to present pulsed tones
Ascend in 5 dB steps for patients with threshold at or
below 50dBHL
Ascend in 2 dB steps for patients with thresholds
above 50dBHL
Determine the patient’s LDL, which is the level
that they rate as #7, uncomfortably loud
Repeat twice at each frequency and take the
average LDL for the three trials
Common LDL frequencies are .5, 1, 2, 3, and 4 kHz
If you are pressed for time, .5 and 3 kHz will provide
you with good, useable information
17. Converting dB HL to dB SPL (real-
ear)
When measuring LDLs on the audiometer, the
LDL will be in dBHL; however, hearing aid output
is in dB SPL
You CANNOT make a direct comparison of the
patient LDL in dB HL to the hearing aid MPO in dB
SPL
Remember, 0dBHL at 1000 Hz
(headphones)=7dBSPL in the open soundfield. This is
referred to as the RETSPL, which stands for real-ear
threshold in sound pressure level.
But, what is that dB level when there is a hearing aid
in the ear, which decreases the physical
volume/space of the ear canal and increases the
18. Converting dB HL to dB SPL (real-
ear)
The conversion formula is as follows:
LDL in real-ear SPL=LDL in HL + RETSPL +
RECD
Refer to the Audiology Online presentation: “How
Loud is Too Loud? Using Loudness Discomfort
Level Measures for Hearing Aid Fitting and
Verification, Part 2”
http://www.audiologyonline.com/audiology-
ceus/course/loud-too-using-loudness-discomfort-
18825
21. Real-Ear-to-Coupler Difference
(RECD)
Ideally, you would measure the patient’s
individual RECD . However, it is usually safe
to use average RECD values.
Average RECD values are provided below
from Dr. Mueller’s AO presentation:
22. Average REDD Values
RETSPL + RECD=REDD (real-ear-to-dial
difference)
I’ll make it very simple for you. Take your LDL
in dB HL and add the average REDD values
(adult) below to arrive at your LDL in dB SPL in
the real-ear!500 Hz 1000 Hz 2000 Hz 3000 Hz 4000 Hz
Headphon
es (TDH
39)
15.5 15.0 16.0 18.0 22.5
3A Inserts
(HA-1)
10.0 8.0 9.5 10.5 13.0
23. Finally…
After you’ve confirmed the patient LDLs and
transformed the LDL in HL to real-ear SPL, you
may compare the patient’s LDLs to the real-ear
saturation response (RESR-90) when you are
performing real-ear testing.
If the RESR-90 exceeds the patient’s LDL at any
frequency, you should reduce the maximum
power output (MPO) of the hearing aid at the
corresponding frequencies.
