Search

This paper describes a compact and extensible marine autonomous passive acoustics recording system, called ROCKHOPPER. The low-noise recorder features a depth rating of 3,500 m and is capable of continuously collecting high-frequency (197 kHz, 24 bits) acoustic data for up to seven months. Because of its small form factor, the ROCKHOPPER can be deployed and recovered by a single person from small vessels, including rigid-hulled inflatable boats (RHIBs). The performance of the instrument was comprehensively evaluated during an offshore deployment in U.S. waters of the northern Gulf of Mexico. Specifically, the analysis encompassed acoustic data collected with five ROCKHOPPER units between May and November 2019. During this period, tropical storm Barry moved through the deployment area, which provided a unique opportunity to study the impacts of a tropical cyclone on the underwater soundscape.

The dependence of a tuning-fork quartz crystal oscillator's frequency f on temperature T is observed over the temperature range −5 to 20°C. From this, a parabolic f(T) function is fit to the crystal's data, and used to compensate for sampling period drift in an Analog to Digital Converter (ADC) system based around this crystal at various temperatures. Resolution and uncertainty of this method are discussed.

Publisher Summary This chapter explores various forms of controllers available from semiconductor manufacturers. The simplest form of a control circuit is variable frequency/constant on-time or pulse frequency modulation (PFM). The basic circuit of a current mode pulse width modulation (PWM) controller in a boost converter has two control loops. The outer loop measures the output voltage and provides an error signal to the inner loop. The inner loop compares the error signal and an analog of the inductor current to decide when to turn off the switch. The effect is to change the pulse width. The operation of the current mode controller has several advantages over a voltage mode controller. One of them is that the inductor current is a direct function of the error voltage, so for small signal analysis, the inductor can be replaced by a voltage controlled current source. This removes one order from the transfer function.

Using multiple acoustic sensors in an array for estimating sound source location relies on time synchrony among the devices. When independent time synchrony methods—such as GPS time stamps—are unavailable, the precision of the time base in individual sensors becomes one of the main sources of error in synchrony, and consequently increases the uncertainty of location estimates. Quartz crystal oscillators, on which many acoustic sensors base sampling rate timing, have a vibration frequency that varies with temperature f(T). Each oscillator exhibits a different frequency-temperature relationship, leading to sensor-dependent sample rate drift. Our Marine Autonomous Recording Units (MARUs) use such oscillators for their sample rate timing, and they experience variations in temperature of at least 20°C between preparation in air and deployment underwater, leading to sample rate drift over their deployments. By characterizing each MARU’s oscillator f(T) function, and measuring the temperature of the MARU during ...

I share much of the Lees' concern about the inadequacy of the Society's efforts to expand academic opportunities and protect the jobs of minorities, radicals, and other "deprived" groups. In the past, a major reason for this inadequacy may have been the inability to recruit into the Society a substantial number of members from most of these groups. Perhaps even more important has been the underrepresentation of these groups in the leadership of SSSP. Among the groups specified by the Lees, only women have comprised a significant proportion of our membership and until recently they too were grossly underrepresented in leadership roles (although not nearly as underrepresented as in most professional organizations, e.g., the ASA). During the past two or three years, as women have become considerably more active in positions of leadership and responsibility in SSSP, there has been a parallel increase in the content on problems of women in society at our annual meetings and in our journal. There is every reason to believe that in the near future, attention will be directed to the special problems of women in academia. Similarly, there has been a noticeable increase in the participation of our younger and more radically oriented colleagues in positions of responsibility during the past two years. This is most apparent in the leadership of several of our divisions and the nominees for the 1976 general elections of SSSP. Again, this trend has been reflected in the content of our meetings and in our journal. Moreover, both of the above trends are reflected in the establishment of a Committee on Unemployment in the Profession, specifically charged, among other things, with considering what action the Society might take about problems of unemployment among minority and politically radical social scientists. I am much less optimistic about the progress the Society has made in focusing on the employment of blacks and other racial and ethnic minority groups in our profession. Certainly in recent years, there has been no appreciable increase in participation of minority members in SSSP, and most certainly no significant change in their participation in leadership positions. The only offices held by blacks in recent years have been appointive and the few blacks nominated to elective positions have been defeated by much better known, white opponents. The only Special Problems Division that has elected black chairpersons has been Intergroup Relations (and that itself might well be taken as tokenism). It should be of considerable concern that SSSP has been ignored by the Black Caucus, an effective force in sensitizing the ASA to the need for more adequate black representation in leadership roles. The participation in SSSP of other racial or ethnic groups, such as American Indians or Spanish-speaking minorities, is virtually nonexistent. Until the Society has actively drawn minorities into leadership roles, little will be done to address ourselves to problems related to their tenuous status in academia. The impetus must come from those who are most concerned. The Society, however, must provide a channel for expressing that concern through real affirmative efforts to draw minority members into leadership roles both in the Society as a whole and within the various divisions. The exploitation of graduate students is a distressing problem and, as the Lees note, one SSSP has not addressed. Certainly, most graduate students, faced with the economic necessities of survival in academia, have too often been forced to sell themselves into a voluntary servitude. Our colleagues (perish the thought that any of us would engage in such practices) are too prone to regard their teaching and research assistants paternalistically as apprentices

A fifth purpose of the Society is to give its attention to conditions that facilitate the work of students of social problems. Outstanding among these are freedom of research and freedom of teaching. Workers in this field are peculiarly open to attack by representatives of vested interests and of reactionary groups. They need the strong defense that comes from the objectivity and high standards of their research. They require the protection of our traditional American guarantees of freedom of speech and inquiry ...