PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

The detection of the first and last pulses in a periodic pulse train: therole of temporal integration and masking
Liudmila RIMSKAYA-KORSAKOVA1; Dmitry NECHAEV2
1
2

N.N. Andreyev Acoustics Institute, Russia

A.N. Severtsov Institute of Ecology and Evolution, Russia

ABSTRACT
A pulse train containing 12 pulses with inter-pulse intervals of 20 to 110 ms was considered a model of thetest and masking phonemes. The first or last pulse of the train varied in level; they were considered tests tomeasure the threshold difference between the test pulse alone and the same pulse in the train (dIso) and theminimum inter-pulse interval (Tmin) for the test pulse detection. The lowest Tmin and dIso were found innormal-hearing listeners. Higher dIso were found in listeners with prolonged temporal integration of periodic
sounds independently of hearing sensitivity. Increased dIso (up to approximately 20 dB) were observed atTmin despite of the test pulse position in the pulse train. The detection properties of the first and last pulses
were supposed to be closely related to the well-known effects of partial masking of loudness and forwardmasking. Thus, within-train pulses affected the detectability of the first and last pulses. It is suggested that
this effect is one of causes of changes in phonemes loudness and the speech intelligibility reduction.
Keywords: partial masking, forward masking, single pulse, pulse train, phonemes loudness, speech
intelligibility

1. INTRODUCTION
The increasing of speech rate may result in reduction of speech intelligibility. This effect can berelated with auditory temporal processing, but not with auditory sensitivity (1,2).
A speech can be considered a sequence of phonemes. It has been supposed (3) that an increase of
the speech rate reduces the understanding of phonemes in a stream of other phonemes, and impairmentof temporal discrimination of phonemes loudness can be a reason of the reduction speech
intelligibility.
The consonant phonemes play a general role in speech intelligibility. The most of them have thefrequency range from 1 to 5 kHz, short duration (10-70 ms) and rather low intensity. A speaker canpronounce 9-14 phonemes per second in normal speech rate which corresponds to phoneme period of
110-70 ms.
The high frequency pulse can be used as a model of consonant and the pulse train as a model of asequence of consonants (1,2). Estimate of loudness detection of a single pulse in a pulse train with may
help to understand the role of consonants loudness in intelligibility of the fast speech. For this purpose,
we investigated conditions where loudness is a cue for detection of a single pulse in a train. We
estimated the dependence of loudness detection of the first and last pulses on the inter-pulse interval inthe train. We looked at indicators that could be characteristics of the auditory temporal processing ofsounds; including speech. The loudness of the sound signal is related to auditory temporal integration
process. Because of this the indicators were matched with temporal integration properties for tones andpulse train as well as with detection threshold of single pulse.
We expected that changes in the loudness of the first and last pulses would be associated with theknown effects of both partial masking of loudness (4) and forward masking (5).

125814lkrk@mail.ru
dm.nechaev@yandex.ru2. PSYCHOACOUSTIC MEASUREMENT
2.1 Methods
The psychoacoustical experiments were carried out in a sound attenuating booth. The
hardware-software complex was used for generation sounds, experimental control and collection data.
One probe contained two sounds (reference and target) with 500 ms pause. The sounds weregenerated digitally online and played back in random order. The probes were digital/analog convertedusing E-MU 0204 USB with sampling rate 44.1 kHz. The analog signals were played monaurally
through HD-265 headphones (Sennheiser, Wedemark, Germany).
The temporal profiles of all pulses were identical. The central frequency of the pulses was 4 kHz
and bandwidth was 240 Hz (less than the critical band). The reference stimuli contained 11 identicalpulses. The target stimuli contained 11 reference pulses plus one test pulse. All listeners couldn’t
discriminate the durations of reference and target stimuli containing 11 or more pulses. Thus, only thepulse loudness could be a cue for detection of the test pulse.
The two experimental paradigms were used: with the test pulse was either before or after pulse train(Fig. 1).

Figure 1. – Temporal diagrams with the test pulse before the pulse train (left) and after the pulse train (right).
Im - amplitude of the train pulses, Is – amplitude of test pulse
The level of pulses in the train was 80 dB SPL. The level of the test pulses varied. The inter-pulseinterval T in the pulse train varied from 20 to 110 ms.
The method of constant stimuli was used to obtain the psychophysical curves or the dependence ofcorrect detection of test pulse on its intensity. Each level of the test pulse was presented 10 times, thelevels alternating randomly. The level of the test pulse that provided a probability of 75% correct
detection was assessed the threshold. We measured two parameters: the minimal inter-pulse interval(Tmin) in which the listeners detected the test pulse, and the difference (dIso) between the test pulse
detection threshold and detection threshold of single pulse (dIso=MinIs-Min0Is, where Min0Is – thedetection threshold of single pulse, MinIs – the detection threshold of the test pulse in pulse train).
We assumed that the indicator Tmin can characterize the temporal resolution of test pulse loudness
in the train; the indicator dIso – changes in the loudness of the test pulses when inter-pulse interval T
was near Tmin.
The indicators Tmin and dIso were compared with the temporal integration of tones and a sequenceof pulses, as well as with the detection threshold of single pulses. A two-alternative forced-choiceprocedure combined with adaptive “two-down, one-up” stimuli trial-by-trial variation was used for
determining the detection thresholds of single pulses, tones and pulse trains.
The difference between detection thresholds for tones of the some duration and tone with durationof 240 ms was used as indicators of temporal integration for tones (I_t). The tone duration was varied
from 15 ms to 240 ms.
The difference between the detection thresholds for the single pulse and the pulse trains was used asindicators of train temporal integration for periodic sounds (I_ps). The inter-pulse interval in the train
was 20, 30, 50, or 80 ms, therefore the train duration with 11 pulses was 200, 300, 500, or 800 ms.
2.2 Listeners
Four listeners with normal hearing (L1, L5, L6, L7) and one listener with aging-related hearing loss
(L2) participated in the study. The information about listeners (age, gender, experience in
psychophysical experiments, and the detection threshold of single test pulse) is presented in table 1.
The results of L1, L6, L7 were averaged and denoted as typical listener (Lt), L5 was denoted as
untypical.

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Table 1 – information about listeners
Listener

AgeGenderThresholdexperience; *- amateur musician

L135

M

17 dB

>60 hour *L535

M16 dB

Without experience *L625

F

10 dB

>20 hour

L735

M

15 dB

<20 hour *

L265

F

26 dB

>60 hour

2.3 Results
Psychophysical curves which are dependences of test pulse detection on relation between levels of
test pulse, Is, and intensity of pulse train, Im, are presented in Fig. 2.
abFigure 2. – Dependent of correct detection of test pulse on ratio of the test pulse level to pulse train level. (a)test pulse before the pulse train (b) test pulse after the pulse train. Data for “typical” listeners with normalhearing (Lt), “untypical” listener with normal hearing (L5) and listener with aging-related hearing loss (L2).
Legend: detection test pulse without pulse train (silent) and different values of T5816

The values of Tmin were different for different listeners and depended on position of the test pulsein the pulse train. The lowest Tmin (25ms) was found for the typical listeners (Lt) at all position of thetest pulse. The listeners L5 and L2 had different thresholds depending on the test pulse position. If thetest pulse was before the pulse train, Tmin was 80 and 50 ms, resp. If the test pulse was after pulse train,
Tmin was 50 and 30 ms, resp. However, the detection thresholds for single pulse were similar forlisteners Lt and L5 and lower for listeners L2. Thus, the temporal resolution threshold, Tmin, for thetest pulse loudness was not associated with the detection thresholds for single pulse.
The maximal values of the dIso were found for T equal to Tmin. Increasing T over Tmin caused
decreasing dIso for all listeners. We suppose that the dIso could be related to changes of test pulse
loudness.
For listener Lt, the highest dIso was 27 dB at T=25 ms, when the test pulse was after pulse train.
When the test pulse was before pulse train, dIso was 9 dB.
The listener L5 had dIso about 23 dB at T=50 ms, when the test pulse was after pulse train and 23
at T=80 ms when the test pulse was before pulse train.
The listeners L2 had dIso about 14 dB at T=30 ms, when the test pulse was after pulse train, and 17
dB at T=50 ms, when test pulse was before pulse train.
The values of dIso and Tmin were not related to the auditory sensitivity of the listeners. The highest
Tmin and dIso were found in “untypical” listener L5. The lowest Tmin and dIso was found innormal-hearing listeners.
Table 2. – The values of threshold shifts dIso
Listener

Start of sequence

End of sequence

dIso, dBdIso, dB2592750

9980

3450-2380

23811021430-

1450

17168026Т, msLt

L5L2The next stage of the study was the comparison of values Tmin and dIso with the indicators oftemporal integration for tones and trains. The detection thresholds of different duration tones and 11pulse trains were presented in tables 3 and 4.
The indicators of I_t were similar for Lt and for L5 and lower for L2. The listener withaging-related hearing loss had decreased of temporal integration.
Table 3. – Indicators of temporal integration for tone

LtThreshold fortone withduration 240 ms,dB
3,9

11,3

7,4

4,9

1,5L50,9

10,98,0

5,0

3,0L2

15,0

7,4

5,92,60,7Listeners

15Tone duration (D_t), ms
30
60

120

Indicators of temporal integration for tones, I_t, dB5817

The indicator of I_ps was approximately matched the detection thresholds of single pulse for Lt.
Thise indicator were varied within 2 dB for T from 20 to 80 ms. This may identify to weak summationof pulse train.
The indicator of I_ps decreased by 5-6 dB with increasing inter-pulse interval from 20 to 80 ms forlistener L5. However, for the listeners L2, the indicator of I_ps was 6 – 8 dB at all T, finding
remarkable summation of pulse train.
Table 4. – Indicators of temporal integration for pulse train.
Listeners

Pulse
detection
threshold, dB

Inter-pulse interval for 11 pulse train, ms
20305080

Indicator of temporal integration for trains, I_sp, dB

Lt

14,00,9

1,80,3-0,6L5

16,0

9,5

9,1

6,9

4,9

L2

26,0

7,7

6,4

8,57,9Temporal integration for tones did not correspond to temporal integration for trains. The listeners
Lt featured the decrease in temporal integration for train in comparison with the listeners L5 and L2.
This suggests that the reason of Tmin and dIso inter-individual difference is the difference in temporal
integration of pulse trains.
Integration of pulse train with inter-pulse intervals of 20-80 ms and train durations of 200-800 ms
was obtained for listeners L5 and L2, but integration of tones with the same duration was absent.
It can be assumed that the integration of train, but not the integration of tones, determines thetemporal resolution of the test pulse loudness.
Thus, the positive values of dIso were found in all position of pulse at T near Tmin. The lower Tmin
was found in listeners with normal hearing. The high Tmin was found for listeners with different
auditory sensitivity but with temporal integration for pulse train having inter-pulse interval of 20-80
ms.

3. Discussion and conclusions
In our experiments, listeners could detect the test pulse only basing on its loudness. We supposethat the minimal inter-pulse interval at which the listener could detect the test pulse (Tmin) can define
the temporal resolution of pulse loudness. Another parameter, the shift of pulse detection thresholds(dIso) may characterize the change of test pulse loudness in pulse train.
The temporal resolution of pulse loudness equal to 25 ms for the typical listeners with normal
hearing (Lt) corresponded to the amplitude modulation frequency threshold for noise, which obtainedusing temporal modulation transfer function (6). The auditory system is considered to analyze
amplitude changes of sound signals if the modulation frequency is less than the modulation threshold.
The listeners with aging-related hearing loss have lower sensitivity to amplitude modulation (7-10). In
our study, the listener with aging-related hearing loss (L2) has the high Tmin.
The temporal integration of tones in our listeners with normal hearing (Lt and L5) and with small
hearing losses (L2) corresponded to the well-known data (11-14).
The temporal integration of pulse trains obtained for “typical” listeners (Lt) with normal hearing,
revealed known properties (15), but the individual data of the two other listeners (I5 and I2) withdifferent auditory sensitivity did not. For them, the indicator of I_ps at T of 20 ms was 6-8 dB. The
auditory system of these listeners could unite the responses on the pulses in train, therefore thedetection thresholds of the train was less than the detection threshold of a single pulse.
The listeners of L5 and L2 had the different values of Tmin for different positions of test pulses intrain. In the case of different positions of the test pulse, the shifts of dIso obtained for inter -pulseinterval equal to Tmin could exceed 20 dB, but connections between the indicators of Tmin and theshifts of dIso were different. These pointed out to the differences in the processes of the loudness
formation for first and last pulses.
For the first pulse in the train, the following rule was true: the higher the value of Tmin the greater
the shift dIso. Apparently, the relatively short-term integration process (with time constant less than5818

110 ms) participated in the formation of the first pulse loudness. This process was responsible for thepartial masking of the pulse loudness (4, 5).
For the last pulse in the train, another rule was valid: the smaller the value of Tmin, the greater theshift of dIso. We supposed, in addition to the short-term integration process, a long-term integration
process of the post-spike changes in the auditory neuron excitability participated in the formation of
the last pulse loudness. This long-term process could be responsible for both the forward masking (5)and changes in loudness of last pulse. The contribution of long-term process to the last pulse detection
could be considerably greater than the contribution of the short-term process.
Thus, the detectability of the threshold loudness of the first and last pulses in train depended on theinter-pulse interval. Due to this it is possible to suppose that the phoneme loudness may depend on
speech rate. Decrease phoneme loudness may be a reason for a decrease in speech intelligibility.

ACKNOWLEDGEMENTS
Supported by the Russian Foundation for Basic Research (RFBR, grants No 14-04-00155 and17-04-00096).

REFERENCES
1. Fitzgibbons PJ, Gordon-Salant S. Age-related differences in discrimination of temporal intervals in
accented tone sequences. Hearing Research. 2010. 264. p. 41–47.
2. Fitzgibbons PJ, Gordon-Salant S. Age effects in discrimination of repeating sequence intervals. J Acoust
Soc Am. 2011. 129. p. 1490-1500.
3. Miller J, Aibel IL, Green K. On the nature of rate-dependent processing during phonetic perception.
Perception and Psychophysics. 1984. 35. p. 5-15.
4. Fastl H. Temporal partial masking of pure tones by broad-band noise: Experimental result and models.
Acta Acustica united with Acustica. 1984. 54. p. 145-153.
5. Fastl H, Zwicker E. Psychoacoustics: Facts and Models. 2008. Springer.
6. Viemeister NF. Temporal modulation transfer functions based upon modulation thresholds. J Acoust Soc
Am. 1979. 66. p.1364-138
7. Formby C. Modulation threshold functions for chronically impaired Meniere patients. Audiology. 1987.
26. p. 89-102.
8. Bacon SP, Viemeister NF. Temporal modulation transfer functions in normal-hearing andhearing-impaired listeners. Audiology. 1985. 24. p.117-134.
9. Bacon SP, Gleitman RM. Modulation detection in subjects with relatively flat hearing losses. Journalof Speech and Hearing Research, 1992. 35. p., 642-653.
10. Moore BCJ, Shailer MJ, Schooneveldt GP. Temporal modulation transfer functions for band-limited
noise in subjects with cochlear hearing loss. British Journal of Audiology. 1992. 26. p. 229-237
11. Green DM, Birdsall TG, Tanner WP. Signal detection as a function of signal intensity and duration, JAcoust Soc Am. 1957. 29. p. 523–531.
12. Zwislocki JJ. Theory of temporal auditory summation. J. Acoust. Soc. Am. 1960, 32, P.1046-1060;
13. Elliott LL. Temporal and masking phenomena in persons with sensorineural hearing loss. Audiology.
1975. 14. p. 336–353.
14. Florentine M, Fastl H, Buus S. Temporal integration in normal hearing, cochlear impairment, andimpairment simulated by masking. J Acoust Soc Am. 1988. 84. p. 195-203.
15. Garner WR, Miller GA. The masked thresholds of pure tones as a function of duration. J Exp Psychol.
1947. 37. p. 293-303.

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