Without properly hearing the transient content on the original recording, your playback will lack the detail and power that was captured.
This week we look into the effect of poor articulation on tonal transients. These are sonic events that help to give instruments their “voice” and provide the intimacy and impact that make live music events so captivating. After all, the pinnacle of high-end music reproduction is achieving the convincing illusion that “you are there!”
A musical line…
is characterized as a rapid staccato of complex tone bursts. Music is then a set of musical lines, overlaid and intertwining one another. The basic element of this woven fabric of music is the tone burst. The acoustic descriptor that relates to musical articulation may well be the tone burst, indeed a rapid staccato of bursts. Figure 1 shows several tone bursts, each separated by a dwell time. We use here a 50% duty cycle: 60 ms on and 60 ms off.
Figure 1: Waveform Representation of Modulated Tone Bursts
we only desire measurement of the signal envelope and the faithfulness of its modulated transmission. Figure 2 shows the source test signal as seen by a dB meter. If each burst is clean and each dwell period quiet, the dB meter output will alternate between loud and quiet levels. The signal rises in the presence of a burst and falls during the dwell time.
Figure 2: SPL vs Time Representation of Modulated Tone Bursts
A closeup of consecutive tone bursts…
shows substantial acoustic energy can occupy the dwell period. Figure 3 shows four bursts in 0.8 seconds played and recorded in a real room. Notice how the bursts are deformed. What used to be a sharp attack, flat sustain and abrupt decay has been turned into a pulse that has lost distinctive features.
Ramps, both up and down, take the place of the sharp attack and decay of the articulate signal. The sustain does not hold flat, it is foreshortened by the ramping transitions. In this inarticulate space, the room mumbles, slurs and often will “double-tongue” the rapidly gated signal. Distorted attack transients will obscure the unique character of instruments and timing of the rhythmic event.
Figure 3: Waveform Representation of Modulated Tone Bursts in a Real Room
Equally important is the subjective aspect
The auditor in a precision listening setting can play the test signal over headphones and hear the rapid, clean staccato of tone bursts whose frequency is slowly varied. The auditor expects the room acoustic to play this signal accurately. By removing the headphones and listening to the same signal in the playback room, defects in the transmission path become quite audible.