Speech Intelligibility Enhancer
Used - Guranteed To Work Perfectly
Offer +++ I Am Very Flexible!
Dee Justesen -
Speech Intelligibility Enhancer
4 Frequency Range Controls
Stereo Audio Filter Input/Output
Comment from: Martin F. Jue, K5FLU President
and Founder MFJ Enterprises, Inc.- As I got older, my high frequency
hearing loss was destroying my ham radio for me..."
I know I'm not the only ham who cant understand all the speech in a
QSO caused by high frequency hearing loss. I developed a solution
that I want to share with my fellow hams.
I almost gave up my ham radio hobby. I have been a passionate
ham radio operator for over 40 years ever since I was a teenager. I
loved every minute of it. Still do, but I almost had to give it up.
As I grew older (Im 56 now) I found myself asking "What did you
say?" so often it got downright embarrassing. I can hear pretty good
most of the time. I just cant always understand what people are
saying and my left ear is weaker than my right ear. It got to where
I was having trouble carrying on QSOs. I could hear, but I just
couldnt quite make out all the words. My hearing problem almost put
a stop to my lifelong hobby. There was no way I was going to give up
Research showed me what to do: I searched the literature and
spoke to hearing and speech experts. According to their
research on intelligibility of speech in hearing English words:
1.The frequencies important for speech intelligibility are the
consonant sounds from 500 to 4000 Hz. They contribute 83% of word
intelligibility. Frequencies from 500 to 1000 Hz contributes 35% of
word intelligibility and 35% of sound energy. Frequencies from 1000
to 4000 Hz contributes 48% of intelligibility but has only 4% of
2. In contrast, frequencies from 125 to 500 Hz contributes 55% of
sound energy but only 4% to word intelligibility. In other
words, nearly half the speech intelligibility is contained in 1000
to 4000 Hz frequency range with only 4% of the speech sound energy.
On the other hand, the low frequencies 125 to 500 Hz have most of
the speech energy but contribute very little to intelligibility.
How I improved my ability to hear and understand QSOs. First,
drastically increase the speech energy above 500 Hz where 83% of
intelligibility is concentrated. Second, drastically reduce the
speech energy below 500 Hz that contributes only 4% of
intelligibility. Amateur radio communications limit audio to about
300 to 2700 Hz. I split the audio band into four overlapping octave
ranges centered at 300, 600, 1200, 2400 Hz. I could boost or cut
each range by nearly 20 db to give me full control. This let me
maximize speech intelligibility for most kinds of frequency loss. My
left ear is weaker than my right ear so I split the output audio
into left and right channels with separate 2.5 watt amplifiers. A
balance control lets me equalize the perceived loudness to each ear.
Now both ears help in improving speech intelligibility!
I couldnt believe my ears! I built one and hooked it to my
rig. I boosted the high frequencies, cut the low frequencies, set
the volume and adjusted the balanced control so I could hear each
side equally loud. I couldn't believe my ears! Speech that I could
hear but barely understand before was now highly understandable. I
got my ham radio back!
With this concept youll understand QSOs better and enjoy rag chewing
and contesting more, even if you dont have high frequency hearing
It helped me so much I wanted to share this with my fellow hams. I
developed this into an accessory that any ham can use. I made it
immune to RFI, added a front panel phone jack, on/off speaker
switch, two selectable transceiver inputs, a bypass switch for
in/out comparison and built into 10" x 2.5" x 6" inch aluminum
enclosure. Needs 12 VDC.