How do I increase my phone intelligibility?

Question

Listening to various operators at different times, I've sometimes noticed, especially during contests, that some operators are easier to understand than others, and it doesn't all seem to be due to their speech patterns. The audio doesn't sound good but it's easy to understand.

At other times I've listened to two operators ragchew for longer periods of time, and while the audio is understandable, it is easier to listen to.

It seems to me that operators have a lot of control over how they sound over the air.

What makes these two sounds so different?

How do I adjust my transmitter to make these two sounds - one focused on intelligibility, and one focused on good/comfortable listening?

Answer 1

Microphone technique has a good bit to do with clarity.

• Talk across the mic, not directly into it, unless it is a noise canceling type designed to be used that way.

• Speak no more than 2" away from the mic, even if it is a desk mic or a boom mounted type; many people make the mistake of thinking that just because they have a desk or boom mounted mic that they can sit back at arm's length (or more) and just turn up the gain on the transmitter. (No one wants to hear a lot of background noise unless necessary.)

• Speak clearly and consistently (take a lesson from the professional radio announcers [not necessarily the DJs]); keep an even and level tone.

• If your transmitter or transceiver has an "ALC" function as part of its metering system, watch that function while you are transmitting; keep your voice peaks within the ALC range on the meter, especially if using a compressor (about half scale or less is plenty).

• Some of the newer rigs have equalizers built in; get with a friend who knows your natural voice to listen to you while you make adjustments to get the best sound.

Answer 2

Eric Scace, K3NA wrote a two part article for the NCJ a few years back on all the adjustments you can make to your audio chain to improve it's quality.

While the article focuses on audio quality for contesting, I think most of the points are relevant "regular" phone contacts. He has 6 main areas that he addresses:

• Operator training — Things like posture, speaking volume, how to speak into a microphone, etc.
• Controls affecting the recording of audio signals — focuses on making your contesting macros sound as much like your normal phone as possible to make copying your messages smooth and easy.
• Controls affecting the playback of message to the radio’s audio input jack — more on the above
• Controls used for live speech routed through the soundcard.
• Transmitter mic and speech processor level, and any other internal audio bandwidth, threshold, or equalizer settings.
• Transmitter power output — making sure you don't ruin your hard work by using too much power and distorting the signal.

There's a full copy on his web site: http://www.k3na.org/articles/Transmit%20audio%20adjustment.pdf. Definitely a useful read.

Answer 3

I've found that precise enunciation works better for the former, whereas controlled modulation (consistent volume and slurring over twixt-word gaps) works better for the latter. Neither is is a function of the transmitter.

Answer 4

From this webpage:

TL;DR:

Get rid of the audio below 300-500 Hz*, and then use audio processing (compression) to raise the average power.

*This is accomplished by:

1. Choosing a suitable microphone, and
2. Equalizing the audio (if possible)

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Details:

Audio which is primarily the mid-range portion of the human voice (i.e. 300 to 2400 Hz.) carries better over long distances. (It is also frequency-efficient on crowded bands). The downside is that this type of narrow audio is not as enjoyable to listen to in a ragchew where signals are S9+. The wider audio is more pleasant to listen to for extended periods, but is not good for contesting, DX chasing, or use on crowded bands.

It is therefore good practice to eliminate the low frequencies below about 300 Hz, because intelligible speech does not require the transmission of frequencies lower than 300 Hz. To do so adds practically nothing to intelligibility. Elimination of the frequencies below 200 or 300 Hz removes a large percentage of the high energy speech components that do not contribute to intelligibility. (see Fig. 2-9 below). Such elimination permits the transmitter to concentrate its efforts on only the essential portions of speech power. In practice, this means something like a 3 to 6 dB improvement in system effectiveness, equivalent to doubling or quadrupling its output power even before any speech processing.

To increase the average power of the voice signal without increasing the peak power, … by emphasizing the low-power, high-frequency components of the speech signal, and attenuating the high-power, low-frequency components of the speech signal.

Speech processing (compression) is most useful when we do this!

Figure 2-9 shows power-vs.-frequency distribution in the average human voice over a range of approximately 200 Hz to 3000 Hz. This curve indicates that the greatest concentration of speech power is at low frequencies. Fortunately, it is the low-frequency components of speech which contribute the least to intelligibility since these frequencies generally occur in the vowel sounds. As a result, the low frequencies may be attenuated without undue loss of speech intelligibility. The low-power, high-frequency components present in a voice signal can be pre-emphasized to provide some increase in the average power level of the signal. Since it is the high-frequency components which predominate in the consonant sounds, some emphasis of the high frequencies improves intelligibility. In other words, it's far more important for us to hear the S's, C's and high-frequency sounds like those. If we don't, we may not understand what the guy at the other end is saying!

Wattmeter needle swing:

Our power output meter and/or plate current meter is NOT a reliable indicator of how well the other station hears us! Fig. 2.9 below clearly shows why.

• There is more power in lower-frequency (bass) frequencies, so we observe more meter swing
• There is less power in higher-frequency (treble) frequencies, so we observe less meter swing (unless compressed or processed).

This is only a portion of the article. Much more information --with references-- can be found there.