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Impulse Response

Characteristics:

KLIPPEL R&D System

KLIPPEL QC System

Time windowed impulse response

TRF

QC Standard

Step response

TRF

Energy time curve

TRF


Group delay response

TRF

Excess time delay response

TRF

Constant time delay detection

TRF

QC Standard

The impulse response describes a linear system in the time domain and corresponds with the transfer function via the Fourier transform. The envelope of the impulse response gives the energy time curve which shows the dispersion of the transferred signal. Signal components which have a different group delay, such as the direct sound and the late room reflections, can be separated by applying a selective time window (e.g. Hanning) to the desired component. Applying the Fourier transform to the windowed impulse response gives the amplitude and phase response of the selected components. The width and the shape of the time window affects the spectral resolution of the selected component in the frequency domain.

KLIPPEL R&D SYSTEM (development)

Module

Comment

Transfer Function Module (TRF)

TRF is dedicated for the measurement of the impulse response by using a sinusoidal sweep (chirp) as stimulus and by performing a two-channel data acquisition. In the small signal domain the impulse response is independent of the stimulus' properties (spectral properties). A variety of tools for post-processing is provided (windowing, smoothing, time-frequency transformation, …).

KLIPPEL QC SYSTEM (end-of-line testing)

Module

Comment

QC Standard: SPL Task; SPL+IMP Task

SPL and SPL+IMP Task measure the delay caused by microphone distance and compensate automatically this delay when calculating results. The delay is shown as time delay and distance.

System Task (Preview)

SPL Measurement Task measures the impulse response the system under test using a sinusoidal sweep with speed profile and amplitude shaping. The spectral and temporal properties of the stimulus have no influence on the measured impulse response as long as the device under test behaves linearly and the signals are measured at sufficient SNR. 

The figure above shows the energy time curve calculated by the Transfer Function Module (TRF) as a grey curve and the windowed part in red. This display is useful to separate the direct sound from later reflections and to set the windows properly. The impulses at the end of the impulse response correspond with the harmonic distortion separated from the linear impulse response.
The figure above shows the energy time curve calculated by the Transfer Function Module (TRF) as a grey curve and the windowed part in red. This display is useful to separate the direct sound from later reflections and to set the windows properly. The impulses at the end of the impulse response correspond with the harmonic distortion separated from the linear impulse response.

Templates of KLIPPEL products

Name of the Template

Application

TRF Scanning Cone Vibration

Manual scanning of cone vibration using a laser sensor with high cut-off frequency (>15 kHz)

TRF sensitivity (Mic 2)

Calibration of the microphone at IN2 using a pistonphone

TRF SPL + harmonics

Standard measurement for fundamental component (SPL) and harmonic distortion

TRF SPL + waterfall

Sound pressure level and cumulative decay spectrum

TRF true acoustical phase

Total phase without time delay

TRF cumulative decay

Cumulative spectral decay

Diagnost. MIDRANGE Sp1

Comprehensive testing of midrange drivers with a resonance 30 Hz < fs < 200 Hz using standard current sensor 1

Diagnost. RUB&BUZZ Sp1

Batch of Rub & Buzz tests with increased voltage (applied to high power devices)

Diagnostics MICROSPEAKER Sp2

Comprehensive testing of microspeakers with a resonance 100 Hz < fs < 2 kHz using sensitive current sensor 2

Diagnostics TWEETER (Sp2)

Comprehensive testing of tweeters with a resonance 100 Hz < fs < 2 kHz using sensitive current sensor 2

Diagnostics VENTED BOX SP1

Comprehensive testing of vented box systems using standard current sensor 1

Diagnostics WOOFER (Sp1)

Comprehensive testing of subwoofers with a resonance 30 Hz < fs < 200 Hz using standard current sensor 1

Diagnostics WOOFER Sp1,2

Comprehensive testing of subwoofers with a resonance 30 Hz < fs < 200 Hz using current sensor 1 and 2

IEC 20.6 Mean SPL

Mean sound pressure level in a stated frequency band according IEC 60268-5 chapter 20.6

IEC 21.2 Frequency Range

Effective frequency range according IEC 60268-5 chapter 21.2

IEC 22.4 Mean Efficiency

Mean efficiency in a frequency band according IEC 60268-5 chapter 22.4

Standards:

  • IEC Standard IEC 60268-5 Sound System Equipment, Part 5: Loudspeakers
  • AES2-1984 AES Recommended practice Specification of Loudspeaker Components Used in Professional Audio and Sound Reinforcement

 

Papers and Preprints:


A. Farina, “Simultaneous Measurement of Impulse Response and Distortion with a Swept-Sine Technique,” presented at the 108th Convention of the Audio Eng. Soc., J. of Audio Eng. Soc. (Abstracts), Volume 48, p. 350 (2000 Apr.), Preprint 5093.

S. Müller, P. Massarani, “Transfer-Function Measurement with Sweeps,” J. of Audio Eng. Soc. 2001, June, Volume 49, No. 6, pp. 443-471.

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